Regulation of Gene Expression Lecture Outline Overview: Differential Expression of Genes • Both prokaryotes and eukaryotes alter their patterns of gene expression in response to changes in environmental conditions. • Multicellular eukaryotes also develop and maintain multiple cell types. ○ Each cell type contains the same genome but expresses a different subset of genes. ○ During development, gene expression must be carefully regulated to ensure that the right genes are expressed only at the correct time and in the correct place. • Gene expression in eukaryotes and bacteria is often regulated at the transcription stage. ○ Control of other levels of gene expression is also important. • RNA molecules play many roles in regulating eukaryotic gene expressions. • Disruptions in gene regulation may lead to cancer. Concept 18.1 Bacteria often respond to environmental change by regulating transcription • Natural selection favors bacteria that express only those genes whose products are needed by the cell. ○ A bacterium in a tryptophan-rich environment that stops producing tryptophan conserves its resources. • Metabolic control occurs on two levels. • First, cells can adjust the activity of enzymes already present. ○ This may happen by feedback inhibition, in which the activity of the first enzyme in a pathway is inhibited by the pathway’s end product. ○ Feedback inhibition, typical of anabolic (biosynthetic) pathways, allows a cell to adapt to short-term fluctuations in the supply of a needed substance. • Second, cells can vary the number of specific enzyme molecules they make by regulating gene expression. ○ The control of enzyme production occurs at the level of transcription, the synthesis of messenger RNA coding for these enzymes. ○ Genes of the bacterial genome may be switched on or off by changes in the metabolic status of the cell. • The basic mechanism for the control of gene expression in bacteria, known as the operon model, was described by Francois Jacob and Jacques Monod in 1961. The operon model controls tryptophan synthesis. • Escherichia coli synthesizes tryptophan from a precursor molecule in a series of steps, with each reaction catalyzed by a specific enzyme. • The five genes coding for the subunits of these enzymes are clustered together on the bacterial chromosome as a transcription unit, served by a single promoter. • Transcription gives rise to one long mRNA molecule that codes for all five polypeptides in the tryptophan pathway. • The mRNA is punctuated with start and stop codons that signal where the coding sequence for each polypeptide begins and ends. • A key advantage of grouping genes with related functions into one transcription unit is that a single on-off switch can control a cluster of functionally related genes. ○ In other words, these genes are coordinately controlled. • When an E. coli cell must make tryptophan for itself, all the enzymes are synthesized at one time. • The switch is a segment of DNA called an operator. • The operator, located within the promoter or between the promoter and the enzyme-coding genes, controls the access of RNA polymerase to the genes. • The operator, the promoter, and the genes they control constitute an operon. ○ The trp operon (trp for tryptophan) is one of many operons in the E. coli genome. • By itself, an operon is turned on: RNA polymerase can bind to the promoter and transcribe the genes of the operon. • The operon can be switched off by a protein called the trp repressor. ○ The repressor binds to the operator, blocks attachment of RNA polymerase to the promoter, and prevents transcription of the operon’s genes. • Each repressor protein recognizes and binds only to the operator of a particular operon. • The trp repressor is the protein product of a regulatory gene called trpR, which is located at some distance from the operon it controls and has its own promoter. • Regulatory genes are transcribed continuously at slow rates, and a few trp repressor molecules are always present in an E. coli cell. • Why is the trp operon not switched off permanently? • First, binding by the repressor to the operator is reversible. ○ An operator vacillates between two states, with and without a repressor bound to it. ○ The relative duration of each state depends on the number of active repressor molecules around. • Second, repressors contain allosteric sites that change shape depending on the binding of other molecules. ○ The trp repressor has two shapes: active and inactive. ○ The trp repressor is synthesized in an inactive form with little affinity for the trp operator. ○ Only if tryptophan binds to the trp repressor at an allosteric site does the repressor protein change to the active form that can attach to the operator, turning the operon off. • Tryptophan functions in the trp operon as a corepressor, a small molecule that cooperates with a repressor protein to switch an operon off. • When concentrations of tryptophan in the cell are high, more tryptophan molecules bind with trp repressor molecules, activating them. ○ The active repressors bind to the trp operator and turn the operon off. • At low levels of tryptophan, most of the repressors are inactive, and transcription of the operon’s genes resumes. There are two types of operons: repressible and inducible. • The trp operon is an example of a repressible operon, one that is inhibited when a specific small molecule (tryptophan) binds allosterically to a regulatory protein. • In contrast, an inducible operon is stimulated (induced) when a specific small molecule interacts with a regulatory protein. • The classic example of an inducible operon is the lac operon (lac for lactose). • Lactose (milk sugar) is available to E. coli in the human colon if the host drinks milk. ○ Lactose metabolism begins with hydrolysis of lactose into its component monosaccharides, glucose and galactose. ○ This reaction is catalyzed by the enzyme ß-galactosidase. • Only a few molecules of b-galactosidase are present in an E. coli cell grown in the absence of lactose. ○ If lactose is added to the bacterium’s environment, the number of ß-galactosidase molecules increases by a thousandfold within 15 minutes. • The gene for ß-galactosidase is part of the lac operon, which includes two other genes coding for enzymes that function in lactose metabolism. • The regulatory gene, lacI, located outside the operon, codes for an allosteric repressor protein that can switch off the lac operon by binding to the operator. • Unlike the trp operon, the lac repressor is active all by itself, binding to the operator and switching the lac operon off. ○ An inducer inactivates the repressor. ○ When lactose is present in the cell, allolactose, an isomer of lactose, binds to the repressor. ○ This inactivates the repressor, and the lac operon can be transcribed. • Repressible enzymes generally function in anabolic pathways, synthesizing end products from raw materials. ○ When the end product is present in sufficient quantities, the cell can allocate its resources to other uses. • Inducible enzymes usually function in catabolic pathways, digesting nutrients to simpler molecules. ○ By producing the appropriate enzymes only when the nutrient is available, the cell avoids making proteins that are not needed. • Both repressible and inducible operons demonstrate negative control of genes because active repressors switch off the active form of the repressor protein. ○ It may be easier to see this for the trp operon, but it is also true for the lac operon. ○ Allolactose induces enzyme synthesis not by acting directly on the genome, but by freeing the lac operon from the negative effect of the repressor. Some gene regulation is positive. • Positive gene control occurs when a protein molecule interacts directly with the genome to switch transcription on. • The lac operon is an example of positive gene regulation. • When glucose and lactose are both present, E. coli preferentially uses glucose. ○ The enzymes for glucose breakdown in glycolysis are always present in the cell. • Only when lactose is present and glucose is in short supply does E. coli use lactose as an energy source and synthesize the enzymes for lactose breakdown. • When glucose levels are low, cyclic AMP (cAMP) accumulates in the cell. • The regulatory protein catabolite activator protein (CAP) is an activator of transcription. • When cAMP is abundant, it binds to CAP, and the regulatory protein assumes its active shape and can bind to a specific site at the upstream end of the lac promoter. ○ The attachment of CAP to the promoter increases the affinity of RNA polymerase for the promoter, directly increasing the rate of transcription. ○ Thus, this mechanism qualifies as positive regulation. • If glucose levels in the cell rise, cAMP levels fall. ○ Without cAMP, CAP detaches from the operon and lac operon is transcribed only at a low level. • The lac operon is under dual control: negative control by the lac repressor and positive control by CAP. ○ The state of the lac repressor (with or without bound allolactose) determines whether or not the lac operon’s genes are transcribed. ○ The state of CAP (with or without bound cAMP) controls the rate of transcription if the operon is repressor-free. ○ The operon has both an on-off switch and a volume control. • CAP works on several operons that encode enzymes used in catabolic pathways. It affects the expression of more than 100 E. coli genes. ○ If glucose is present and CAP is inactive, then the synthesis of enzymes that catabolize other compounds is slowed. ○ If glucose levels are low and CAP is active, then the genes that produce enzymes that catabolize whichever other fuel is present are transcribed at high levels. Concept 18.2 Eukaryotic gene expression is regulated at many stages • Like unicellular organisms, the tens of thousands of genes in the cells of multicellular eukaryotes turn on and off in response to signals from their internal and external environments. • Gene expression must be controlled on a long-term basis during cellular differentiation. Differential gene expression is the expression of different genes by cells with the same genome. • A typical human cell probably expresses about 20% of its genes at any given time. ○ Highly specialized cells, such as nerves or muscles, express a tiny fraction of their genes. ○ Although all the cells in an organism contain an identical genome, the subset of genes expressed in the cells of each type is unique. • The differences between cell types are due to differential gene expression, the expression of different genes by cells with the same genome. • The function of any cell, whether a single-celled eukaryote or a particular cell type in a multicellular organism, depends on the appropriate set of genes being expressed. ○ Problems with gene expression and control can lead to imbalance and disease, including cancer. • Our understanding of the mechanisms that control gene expression in eukaryotes has been enhanced by new research methods, including advances in DNA technology. • In all organisms, a common control point for gene expression is at transcription, often in response to signals coming from outside the cell. ○ For this reason, the term gene expression is often equated with transcription. • With their greater complexity, eukaryotes have opportunities for controlling gene expression at additional stages. Chromatin modifications affect the availability of genes for transcription. • The DNA of eukaryotic cells is packaged with proteins in a complex called chromatin. ○ The basic unit of chromatin is the nucleosome. • The location of a gene’s promoter relative to nucleosomes and to the sites where the DNA attaches to the chromosome scaffold or nuclear lamina affect whether the gene is transcribed. • Genes of densely condensed heterochromatin are usually not expressed. • Chemical modifications of the histone proteins and DNA of chromatin play a key role in chromatin structure and gene expression. • The N-terminus of each histone molecule in a nucleosome protrudes outward from the nucleosome. ○ These histone tails are accessible to various modifying enzymes, which catalyze the addition or removal of specific chemical groups. • Histone acetylation (addition of an acetyl group, —COCH3) and deacetylation of lysines in histone tails appear to play a direct role in the regulation of gene transcription. • Acetylation of lysines neutralizes their positive charges and reduces the binding of histone tails to neighboring nucleosomes, easing access for transcription proteins. ○ Some of the enzymes responsible for acetylation or deacetylation are associated with or are components of transcription factors that bind to promoters. • Thus, histone acetylation enzymes may promote the initiation of transcription not only by modifying chromatin structure but also by binding to and recruiting components of the transcription machinery. • Other chemical groups, such as methyl and phosphate groups, can be reversibly attached to amino acids in histone tails. ○ The attachment of methyl groups (—CH3) to histone tails leads to condensation of chromatin. ○ The addition of a phosphate group (phosphorylation) to an amino acid next to a methylated amino acid has the opposite effect. • The recent discovery that modifications to histone tails can affect chromatin structure and gene expression has led to the histone code hypothesis. ○ This hypothesis proposes that specific combinations of modifications, as well as the order in which they have occurred, determine chromatin configuration. ○ Chromatin configuration in turn influences transcription. DNA methylation reduces gene expression. • While some enzymes methylate the tails of histone proteins, other enzymes methylate certain bases in DNA itself, usually cytosine. ○ DNA methylation occurs in most plants, animals, and fungi. • Inactive DNA is generally more highly methylated than actively transcribed regions. ○ For example, the inactivated mammalian X chromosome is heavily methylated. ○ Individual genes are usually more heavily methylated in cells where they are not expressed. Removal of extra methyl groups can turn on some of these genes. • In some species, DNA methylation is responsible for the long-term inactivation of genes during cellular differentiation. ○ Deficient DNA methylation leads to abnormal embryonic development in organisms as different as mice and the plant Arabidopsis. • Once methylated, genes usually stay that way through successive cell divisions in a given individual. • Methylation enzymes recognize sites on one strand that are already methylated and correctly methylate the daughter strand after each round of DNA replication. • This methylation pattern accounts for genomic imprinting, in which methylation turns off either the maternal or paternal alleles of certain mammalian genes at the start of development. • The chromatin modifications just discussed do not alter the DNA sequence, and yet they may be passed along to future generations of cells. • Inheritance of traits by mechanisms not directly involving the nucleotide sequence is called epigenetic inheritance. • The molecular systems for chromatin modification may well interact with each other in a regulated way. ○ In Drosophila, experiments suggest that a particular histone-modifying enzyme recruits a DNA methylation enzyme to one region and that the two enzymes collaborate to silence a particular set of genes. ○ Working in the opposite order, proteins have also been found that bind to methylated DNA and then recruit histone deacetylation enzymes. ○ Thus, a dual mechanism, involving both DNA methylation and histone deacetylation, can repress transcription. • Researchers are amassing more and more evidence for the importance of epigenetic information in the regulation of gene expression. ○ Epigenetic variations may explain why one identical twin acquires a genetically based disease, such as schizophrenia, while another does not, despite their identical genomes. ○ Alterations in normal patterns of DNA methylation are seen in some cancers, where they are associated with inappropriate gene expression. • Enzymes that modify chromatin structure are integral parts of the cell’s machinery for regulating transcription. Transcription initiation is controlled by proteins that interact with DNA and with each other. • Chromatin-modifying enzymes provide initial control of gene expression by making a region of DNA more available or less available for transcription. • A cluster of proteins called a transcription initiation complex assembles on the promoter sequence at the upstream end of the gene. ○ One component, RNA polymerase II, transcribes the gene, synthesizing a primary RNA transcript or pre-mRNA. ○ RNA processing includes enzymatic addition of a 5¢ cap and a poly-A tail, as well as splicing out of introns to yield a mature mRNA. • Multiple control elements are associated with most eukaryotic genes. ○ Control elements are noncoding DNA segments that serve as binding sites for protein transcription factors. ○ Control elements and the transcription factors they bind are critical to the precise regulation of gene expression in different cell types. • To initiate transcription, eukaryotic RNA polymerase requires the assistance of proteins called transcription factors. • General transcription factors are essential for the transcription of all protein-coding genes. ○ Only a few general transcription factors independently bind a DNA sequence such as the TATA box within the promoter. ○ Others are involved in protein-protein interactions, binding each other and RNA polymerase II. • Only when the complete initiation complex has been assembled can the polymerase begin to move along the DNA template strand to produce a complementary strand of RNA. • The interaction of general transcription factors and RNA polymerase II with a promoter usually leads to only a slow rate of initiation and the production of few RNA transcripts. • In eukaryotes, high levels of transcription of particular genes depend on the interaction of control elements with specific transcription factors. • Some control elements, named proximal control elements, are located close to the promoter. • Distal control elements, grouped as enhancers, may be thousands of nucleotides away from the promoter or even downstream of the gene or within an intron. • A given gene may have multiple enhancers, each active at a different time or in a different cell type or location in the organism. ○ Eukaryotic gene expression can be altered by the binding of specific transcription factors, either activators or repressors, to the control elements of enhancers. • Two structural elements are common to many activator proteins: a DNA-binding domain and one or more activation domains. ○ Activation domains bind other regulatory proteins or components of the transcription machinery to facilitate transcription. • Protein-mediated bending of DNA brings bound activators in contact with a group of mediator proteins that interact with proteins at the promoter. ○ These interactions help assemble and position the initiation complex on the promoter. • Eukaryotic repressors can inhibit gene expression by blocking the binding of activators to their control elements or to components of the transcription machinery. ○ Other repressors bind directly to control-element DNA, turning off transcription even in the presence of activators. • Some activators and repressors act indirectly to influence chromatin structure. ○ Some activators recruit proteins that acetylate histones near the promoters of specific genes, promoting transcription. ○ Some repressors recruit proteins that deacetylate histones, reducing transcription or silencing the gene. • Recruitment of chromatin-modifying proteins seems to be the most common mechanism of repression in eukaryotes. The control of transcription in eukaryotes depends on the binding of activators to DNA control elements. • The number of different nucleotide sequences found in control elements is surprisingly small: about a dozen. • On average, each enhancer is composed of about ten control elements, each of which can bind to only one or two specific transcription factors. ○ The particular combination of control elements in an enhancer may be more important than the presence of a unique control element in regulating transcription of the gene. • Even with only a dozen control element sequences, a large number of combinations are possible. • A particular combination of control elements is able to activate transcription only when the appropriate activator proteins are present, at a precise time during development or in a particular cell type. • The use of different combinations of control elements allows fine regulation of transcription with a small set of control elements. • In prokaryotes, coordinately controlled genes are often clustered into an operon with a single promoter and other control elements upstream. ○ The genes of the operon are transcribed into a single mRNA and translated together. • In contrast, very few eukaryotic genes are organized this way. • More commonly, co-expressed genes coding for the enzymes of a metabolic pathway are scattered over different chromosomes. ○ Coordinate gene expression depends on the association of a specific control element or combination of control elements with every gene of a dispersed group. ○ A common group of transcription factors binds to all the genes in the group, promoting simultaneous gene transcription. • For example, a steroid hormone enters a cell and binds to a specific receptor protein in the cytoplasm or nucleus, forming a hormone–receptor complex that serves as a transcription activator. ○ Every gene whose transcription is stimulated by that steroid hormone has a control element recognized by that hormone–receptor complex. • Other signal molecules control gene expression indirectly by triggering signal-transduction pathways that lead to activation of transcription. ○ The principle of coordinate regulation is the same: Genes with the same control elements are activated by the same chemical signals. • Systems for coordinating gene regulation probably arose early in evolutionary history. • The nucleus has a defined architecture and regulated movements of chromatin. • Recent techniques allow researchers to cross-link and identify regions of chromosomes that associate with each other during interphase. • Loops of chromatin extend from individual chromosomal territories into specific sites in the nucleus. ○ Different loops from the same chromosome and loops from other chromosomes congregate in such sites, some of which are rich in RNA polymerases and other transcription-associated proteins. ○ These sites are likely areas specialized for a common function or transcription factories. Post-transcriptional mechanisms play supporting roles in the control of gene expression. • Regulatory mechanisms that operate after transcription allow a cell to rapidly fine-tune gene expression in response to environmental changes, without altering its transcriptional patterns. ○ RNA processing in the nucleus and the export of mRNA to the cytoplasm provide opportunities for gene regulation that are not available in prokaryotes. • In alternative RNA splicing, different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns. ○ Regulatory proteins specific to a cell type control intron-exon choices by binding to regulatory sequences within the primary transcript. • Alternative RNA splicing significantly expands the repertoire of a set of genes. ○ It may explain the surprisingly low number of human genes: similar to those of a soil worm, a mustard plant, or a sea anemone. ○ Between 75% and 100% of human genes that have multiple exons probably undergo alternative splicing. ○ The extent of alternative splicing increases the number of possible human proteins, likely correlated with complexity of form. • The life span of an mRNA molecule is an important factor in determining the pattern of protein synthesis. ○ Prokaryotic mRNA molecules are typically degraded after only a few minutes, while eukaryotic mRNAs typically last for hours, days, or weeks. ○ In red blood cells, mRNAs for hemoglobin polypeptides are unusually stable and are translated repeatedly. • Nucleotide sequences in the untranslated trailer region (UTR) at the 3¢ end affect mRNA stability. ○ Transferring such a sequence from a short-lived mRNA to a normally stable mRNA results in quick mRNA degradation. Translation presents an opportunity for the regulation of gene expression. • The initiation of translation of an mRNA can be blocked by regulatory proteins that bind to specific sequences within the 5¢ or 3¢ UTR of the mRNA, preventing ribosome attachment. • The mRNAs present in the eggs of many organisms lack poly-A tails of sufficient length to allow initiation of translation. ○ During embryonic development, a cytoplasmic enzyme adds more adenine nucleotides so that translation can begin at the appropriate time. • Translation of all the mRNAs in a eukaryotic cell may be regulated simultaneously by the activation or inactivation of the protein factors required to initiate translation. ○ This mechanism starts the translation of mRNAs that are stored in eggs. ○ Just after fertilization, translation is triggered by the sudden activation of translation initiation factors, resulting in a burst of protein synthesis. • Some plants and algae store mRNAs during periods of darkness. Light triggers the reactivation of the translational apparatus. The final opportunities for controlling gene expression occur after translation. • Often, eukaryotic polypeptides are processed to yield functional proteins. ○ For example, cleavage of pro-insulin forms the active hormone. • Many proteins must undergo chemical modifications before they are functional. ○ Regulatory proteins may be activated or inactivated by the reversible addition of phosphate groups. ○ Proteins destined for the surface of animal cells acquire sugars. • Regulation may occur at any of the steps involved in modifying or transporting a protein. • The length of time a protein functions before it is degraded is strictly regulated. ○ Proteins such as the cyclins that regulate the cell cycle must be relatively short-lived. • To mark a protein for destruction, the cell attaches a small protein called ubiquitin to it. ○ Giant protein complexes called proteasomes recognize and degrade the tagged proteins. • Mutations making specific cell cycle proteins impervious to proteasome degradation can lead to cancer. • The scientists worked out the regulated process of protein degradation won the 2004 Nobel Prize in Chemistry. Concept 18.3 Noncoding RNAs play multiple roles in controlling gene expression • Only 1.5% of the human genome codes for proteins. Of the remainder, only a very small fraction consists of genes for ribosomal RNA and transfer RNA. • Until recently, it was assumed that most of the rest of the DNA was untranscribed. Recent data have challenged that assumption, however. ○ Study of a region comprising 1% of the human genome found that over 90% of the region was transcribed. ○ Introns accounted for only a fraction of this transcribed, nontranslated RNA. • A significant amount of the genome may be transcribed into non–protein-coding RNAs (or noncoding RNAs or ncRNAs), including a variety of small RNAs. • A large, diverse population of RNA molecules may play crucial roles in regulating gene expression in the cell. MicroRNAs can bind to complementary sequences in mRNA molecules. • In the past few years, researchers have found small, single-stranded RNA molecules called microRNAs (miRNAs) that bind to complementary sequences in mRNA molecules. • miRNAs are formed from longer RNA precursors that fold back on themselves to form one or more short, double-stranded hairpin structures stabilized by hydrogen bonding. • An enzyme called Dicer cuts each hairpin into a short, double-stranded fragment of about 22 nucleotide pairs. • One of the two strands is degraded. The other strand (miRNA) associates with a protein complex and directs the complex to any mRNA molecules that have a complementary sequence of 7-8 nucleotides. • The miRNA–protein complex either degrades the target mRNA or blocks its translation. • Expression of up to one-half of all human genes may be regulated by miRNAs. • The phenomenon of inhibition of gene expression by RNA molecules is called RNA interference (RNAi). • Injecting double-stranded RNA molecules into a cell somehow turns off expression of a gene with the same sequence as the RNA. ○ This RNA interference is due to small interfering RNAs (siRNAs), similar in size and function to miRNAs and are generated by similar mechanisms in eukaryotic cells. • Both miRNAs and siRNAs can associate with the same proteins, with similar results. ○ The distinction between these molecules is the nature of the precursor molecules from which they are formed. ○ Each miRNA forms from a single hairpin in the precursor RNA, while multiple siRNAs form from a longer, double-stranded RNA molecule. • Cellular RNAi pathways lead to the destruction of RNAs and may have originated as a natural defense against infection by double-stranded RNA viruses. ○ The fact that the RNAi pathway can also affect the expression of nonviral cellular genes may reflect a different evolutionary origin for the RNAi pathway. • Many species, including mammals, possess long, double-stranded precursors to small RNAs that interfere with various steps in gene expression. Small RNAs can remodel chromatin and silence transcription. • Small RNAs can cause remodeling of chromatin structure. ○ In yeast, siRNAs are necessary for the formation of heterochromatin at the centromeres of chromosomes. • An RNA transcript produced from DNA in the centromeric region of the chromosome is copied into double-stranded RNA by a yeast enzyme and then processed into siRNAs. ○ The siRNAs associate with a protein complex, targeting the complex back to the RNA sequences made from the centromeric sequences of DNA. ○ The proteins in the complex recruit enzymes to modify the chromatin, turning it into the highly condensed centromeric heterochromatin. • A newly discovered class of small ncRNAs, called piwi-associated RNAs (piRNAs) also induce formation of heterochromatin, blocking expression of parasitic DNA elements in the genome known as transposons. ○ piRNAs, 24–31 nucleotides in length, are processed from single-stranded RNA precursors. ○ In germ cells of many animal species, piRNAs help re-establish appropriate methylation patterns in the genome during gamete formation. • Chromatin remodeling not only blocks expression of large regions of the chromosome; RNA-based mechanisms may also block the transcription of specific genes. ○ Some plant miRNAs have sequences that bind to gene promoters and can repress transcription; piRNAs can also block expression of specific genes. ○ In some cases, miRNAs and piRNAs activate gene expression. • Small ncRNAs regulate gene expression at multiple steps and in many ways. ○ Extra levels of gene regulation may allow evolution of a higher degree of complexity of form. ○ An increase in the number of miRNAs encoded in the genomes of species may have allowed morphological complexity to increase over evolutionary time. • A survey of species suggests that siRNAs evolved first, followed by miRNAs and later piRNAs, which are found only in animals. ○ While there are hundreds of types of miRNA, there appear to be many thousands of types of piRNAs, allowing the potential for very sophisticated gene regulation by piRNAs. • Many ncRNAs play important roles in embryonic development, the ultimate example of an elaborate program of regulated gene expression. Concept 18.4 A program of differential gene expression leads to the different cell types in a multicellular organism • In the development of most multicellular organisms, a single-celled zygote gives rise to cells of many different types. ○ Each type has a different structure and corresponding function. ○ Cells of different types are organized into tissues, tissues into organs, organs into organ systems, and organ systems into the whole organism. • Thus, the process of embryonic development must give rise not only to cells of different types but also to higher-level structures arranged in a particular way in three dimensions. A genetic program is expressed during embryonic development. • As a zygote develops into an adult organism, its transformation results from three interrelated processes: cell division, cell differentiation, and morphogenesis. • Through a succession of mitotic cell divisions, the zygote gives rise to many cells. ○ Cell division alone would produce only a great ball of identical cells. • During development, cells become specialized in structure and function, undergoing cell differentiation. • Different kinds of cells are organized into tissues and organs. • The physical processes that give an organism its shape constitute morphogenesis, the “creation of form.” • Cell division, cell differentiation, and morphogenesis have their basis in cellular behavior. ○ Morphogenesis can be traced back to changes in the shape and motility of cells in the various embryonic regions. ○ The activities of a cell depend on the genes it expresses and the proteins it produces. ○ Because almost all cells in an organism have the same genome, differential gene expression results from differential gene regulation in different cell types. • Why are different sets of activators present in different cell types? • One important source of information early in development is the egg’s cytoplasm, which contains both RNA and proteins encoded by the mother’s DNA, distributed unevenly in the unfertilized egg. • Maternal substances that influence the course of early development are called cytoplasmic determinants. ○ These substances regulate the expression of genes that affect the developmental fate of the cell. ○ After fertilization, the cell nuclei resulting from mitotic division of the zygote are exposed to different cytoplasmic environments. ○ The set of cytoplasmic determinants a particular cell receives helps determine its developmental fate by regulating expression of the cell’s genes during cell differentiation. • The other important source of developmental information is the environment around the cell, especially signals impinging on an embryonic cell from nearby cells. ○ In animals, these signals include contact with cell-surface molecules on neighboring cells and the binding of growth factors secreted by neighboring cells. • These signals cause changes in the target cells, a process called induction. ○ The molecules conveying these signals within the target cells are cell-surface receptors and other proteins expressed by the embryo’s own genes. ○ The signal molecules send a cell down a specific developmental path by causing a change in its gene expression that eventually results in observable cellular changes. Cell differentiation is due to the sequential regulation of gene expression. • During embryonic development, cells become visibly different in structure and function as they differentiate. • The earliest changes that set a cell on a path to specialization show up only at the molecular level. ○ Molecular changes in the embryo drive the process, called determination, which leads to the observable differentiation of a cell. • Once it has undergone determination, an embryonic cell is irreversibly committed to its final fate. ○ If a determined cell is experimentally placed in another location in the embryo, it will differentiate as if it were in its original position. • The outcome of determination—observable cell differentiation—is caused by the expression of genes that encode tissue-specific proteins. ○ These proteins give a cell its characteristic structure and function. • Differentiation begins with the appearance of cell-specific mRNAs and is eventually observable in the microscope as changes in cellular structure. • In most cases, the pattern of gene expression in a differentiated cell is controlled at the level of transcription. • Cells produce the proteins that allow them to carry out their specialized roles in the organism. ○ For example, liver cells specialize in making albumin, while lens cells specialize in making crystalline. ○ Skeletal muscle cells have high concentrations of proteins specific to muscle tissues, such as a muscle-specific version of the contractile proteins myosin and actin, as well as membrane receptor proteins that detect signals from nerve cells. • Muscle cells develop from embryonic precursors that have the potential to develop into a number of alternative cell types. ○ Although the committed cells are unchanged, they are now myoblasts. ○ Eventually, myoblasts begin to synthesize muscle-specific proteins and fuse to form mature, elongated, multinucleate skeletal muscle cells. • Researchers have worked out the events at the molecular level that lead to muscle cell determination by growing myoblasts in culture and analyzing them with molecular biology techniques. ○ Researchers isolated different genes, caused each to be expressed in a separate embryonic precursor cell, and looked for differentiation into myoblasts and muscle cells. ○ They identified several “master regulatory genes” that, when transcribed and translated, commit the cells to become skeletal muscle. • One of these master regulatory genes is called myoD. ○ myoD encodes MyoD protein, a transcription factor that binds to specific control elements in the enhancers of various target genes and stimulates their expression. ○ Some target genes for MyoD encode for other muscle-specific transcription factors. ○ MyoD also stimulates expression of the myoD gene itself, helping to maintain the cell’s differentiated state. • All the genes activated by MyoD have enhancer control elements recognized by MyoD and are thus coordinately controlled. • The secondary transcription factors activate the genes for proteins such as myosin and actin to confer the unique properties of skeletal muscle cells. • The MyoD protein is capable of changing fully differentiated fat and liver cells into muscle cells. • Not all cells can be transformed by MyoD, however. ○ Nontransforming cells may lack a combination of regulatory proteins in addition to MyoD. Pattern formation sets up the embryo’s body plan. • Cytoplasmic determinants and inductive signals contribute to pattern formation, the development of spatial organization in which the tissues and organs of an organism are all in their characteristic places. • Pattern formation begins in the early embryo, when the major axes of an animal are established. • Before specialized tissues and organs form, the relative positions of a bilaterally symmetrical animal’s three major body axes (anterior-posterior, dorsal-ventral, right-left) are established. • The molecular cues that control pattern formation, positional information, are provided by cytoplasmic determinants and inductive signals. ○ These signals tell a cell its location relative to the body axes and to neighboring cells and determine how the cell and its progeny will respond to future molecular signals. • Studies of pattern formation in Drosophila melanogaster have established that genes control development and have identified the key roles of specific molecules in defining position and directing differentiation. • Combining anatomical, genetic, and biochemical approaches in the study of Drosophila development, researchers have discovered developmental principles common to many other species, including humans. • Fruit flies and other arthropods have a modular construction. ○ An ordered series of segments make up the three major body parts: the head, thorax (with wings and legs), and abdomen. • Cytoplasmic determinants in the unfertilized egg provide positional information for two developmental axes (anterior-posterior and dorsal-ventral axis) before fertilization. • The Drosophila egg develops in the female’s ovary, surrounded by ovarian cells called nurse cells and follicle cells that supply the egg cell with nutrients, mRNAs, and other substances. • During fruit fly development, the egg forms a segmented larva, which goes through three larval stages. ○ The fly larva forms a pupal cocoon within which it metamorphoses into an adult fly. • In the 1940s, Edward B. Lewis used mutants to investigate Drosophila development. ○ Bizarre developmental mutations were on the fly’s genetic map, providing the first concrete evidence that genes somehow direct the developmental process. ○ These homeotic genes control pattern formation in the late embryo, larva, and adult. • In the late 1970s, Christiane Nüsslein-Volhard and Eric Weischaus set out to identify all the genes that affect segmentation in Drosophila. They faced three problems. • First, because Drosophila has about 13,700 genes, there could be either only a few genes affecting segmentation or so many that the pattern would be impossible to discern. • Second, mutations that affect segmentation are likely to be embryonic lethals, leading to death at the embryonic or larval stage. ○ Flies with embryonic lethal mutations never reproduce, and cannot be bred for study. ○ Nüsslein-Volhard and Wieschaus focused on recessive mutations that could be propagated in heterozygous flies. • Third, because of maternal effects on axis formation in the egg, the researchers also needed to study maternal genes. • After exposing flies to mutagenic chemicals, Nüsslein-Volhard and Wieschaus looked for dead embryos and larvae with abnormal segmentation. ○ Through appropriate crosses, they found heterozygotes carrying embryonic lethal mutations. • Nüsslein-Volhard and Wieschaus identified 1,200 genes essential for embryonic development. ○ About 120 of these were essential for normal segmentation. • The researchers grouped the genes by general function, mapped them, and cloned many of them. • In 1995, Nüsslein-Volhard, Wieschaus, and Lewis were awarded a Nobel Prize. Gradients of maternal molecules in the early Drosophila embryo control axis formation. • Cytoplasmic determinants produced under the direction of maternal effect genes are deposited in the unfertilized egg. • A maternal effect gene is a gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the offspring’s own genotype. ○ In fruit fly development, maternal effect genes encode proteins or mRNA that are placed in the egg while it is still in the ovary. ○ When the mother has a mutation in a maternal effect gene, she makes a defective gene product (or none at all) and her eggs will not develop properly when fertilized. • Maternal effect genes are also called egg-polarity genes because they control the orientation of the egg and consequently the fly. ○ One group of genes sets up the anterior-posterior axis, while a second group establishes the dorsal-ventral axis. • One gene called bicoid affects the front half of the body. • An embryo whose mother has a mutant bicoid gene lacks the front half of its body and has duplicate posterior structures at both ends. ○ This suggests that the product of the mother’s bicoid gene is essential for setting up the anterior end of the fly and might be concentrated at the future anterior end. • This is a specific version of the morphogen gradient hypothesis, in which gradients of morphogens establish an embryo’s axes and other features. • Using DNA technology and biochemical methods, researchers were able to clone the bicoid gene and use it as a probe for bicoid mRNA in the egg. ○ As predicted, the bicoid mRNA is concentrated at the extreme anterior end of the egg cell. • After the egg is fertilized, bicoid mRNA is transcribed into protein, which diffuses from the anterior end toward the posterior, resulting in a gradient of proteins in the early embryo. ○ Injections of pure bicoid mRNA into various regions of early embryos resulted in the formation of anterior structures at the injection sites. • The bicoid research is important for three reasons. 1. It identified a specific protein required for some of the earliest steps in pattern formation. 2. It increased our understanding of the mother’s role in the development of an embryo. 3. It demonstrated a key developmental principle: a gradient of molecules can determine polarity and position in the embryo. • Maternal mRNAs are crucial during development of many species. ○ In Drosophila, gradients of specific proteins encoded by maternal mRNAs determine the posterior and anterior ends and establish the dorsal-ventral axis. • Later, positional information encoded by the embryo’s genes establishes a specific number of correctly oriented segments and triggers the formation of each segment’s characteristic structures. Concept 18.5 Cancer results from genetic changes that affect cell cycle control • Cancer is a set of diseases in which cells escape the control mechanisms that normally regulate cell growth and division. ○ The gene regulation systems that go wrong during cancer are the systems that play important roles in embryonic development and immune response. • The genes that normally regulate cell growth and division during the cell cycle include genes for growth factors, their receptors, and the intracellular molecules of signaling pathways. ○ Mutations altering any of these genes in somatic cells can lead to cancer. ○ The agent of such changes can be random spontaneous mutations or environmental influences such as chemical carcinogens, X-rays, and some viruses. Proto-oncogenes can become oncogenes, contributing to the development of cancer. • Cancer-causing genes, oncogenes, were initially discovered in viruses. ○ Close counterparts have been found in the genomes of humans and other animals.å • Normal versions of cellular genes, called proto-oncogenes, code for proteins that stimulate normal cell growth and division. • A proto-oncogene becomes an oncogene following genetic changes that lead to an increase in the proto-oncogene’s protein production or in the intrinsic activity of each protein molecule. ○ These genetic changes include movement of DNA within the genome, amplification of the proto-oncogene, and point mutations in a control element or the proto-oncogene itself. • Cancer cells frequently have chromosomes that have been broken and rejoined incorrectly. ○ A fragment may be moved to a location near an active promoter or other control element. • Amplification increases the number of copies of the proto-oncogene in the cell. • A point mutation in the promoter or enhancer of a proto-oncogene may increase its expression. • A point mutation in the coding sequence may lead to translation of a protein that is more active or longer-lived. • All of these mechanisms can lead to abnormal stimulation of the cell cycle, putting the cell on the path to malignancy. Mutations to tumor-suppressor genes may contribute to cancer. • The normal products of tumor-suppressor genes inhibit cell division. • Some tumor-suppressor proteins normally repair damaged DNA, preventing the accumulation of cancer-causing mutations. • Other tumor-suppressor proteins control the adhesion of cells to each other or to an extracellular matrix, which is crucial for normal tissues and often absent in cancers. • Still others are components of cell-signaling pathways that inhibit the cell cycle. ○ Decreases in the normal activity of a tumor-suppressor protein may contribute to cancer. • The proteins encoded by many proto-oncogenes and tumor-suppressor genes are components of cell-signaling pathways. • Mutations in the products of two key genes, the ras proto-oncogene and the p53 tumor-suppressor gene, occur in 30% and over 50% of human cancers, respectively. • The Ras protein, the product of the ras gene, is a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases. ○ At the end of the pathway is the synthesis of a protein that stimulates the cell cycle. • Many ras oncogenes have a point mutation that leads to a hyperactive version of the Ras protein that trigger the kinase cascade in the absence of growth factor, resulting in excessive cell division. • The p53 gene, named for its 53,000-dalton protein product, is a tumor-suppressor gene. ○ The p53 protein is a specific transcription factor for the synthesis of several cell cycle-inhibiting proteins. ○ The p53 gene has been called the “guardian angel of the genome.” • Once activated by DNA damage, the p53 protein functions as an activator for several genes. ○ The p53 protein can activate the p21 gene, whose product halts the cell cycle by binding to cyclin-dependent kinases, allowing time for DNA repair. ○ p53 also activates expression of a group of miRNAs, which inhibit the cell cycle. ○ The p53 protein can also turn on genes directly involved in DNA repair. ○ When DNA damage is irreparable, the p53 protein can activate “suicide genes” whose protein products cause cell death by apoptosis. • A mutation that knocks out the p53 gene can lead to excessive cell growth and cancer. Multiple mutations underlie the development of cancer. • More than one somatic mutation is generally needed to produce the changes characteristic of a full-fledged cancer cell. • If cancer results from an accumulation of mutations, and if mutations occur throughout life, then the longer we live, the more likely we are to develop cancer. • Colorectal cancer, with 140,000 new cases and 50,000 deaths in the United States each year, illustrates a multistep cancer path. ○ The first sign is often a polyp, a small benign growth in the colon lining. ○ The cells of the polyp look normal but divide unusually frequently. ○ Through gradual accumulation of mutations that activate oncogenes and knock out tumor-suppressor genes, the polyp can develop into a malignant tumor. ○ A ras oncogene and a mutated p53 tumor-suppressor gene are usually involved. • About a half dozen DNA changes must occur for a cell to become fully cancerous. • These changes usually include the appearance of at least one active oncogene and the mutation or loss of several tumor-suppressor genes. ○ Because mutant tumor-suppressor alleles are usually recessive, mutations must knock out both alleles. ○ Most oncogenes behave like dominant alleles and require only one mutation. Cancer can run in families. • The fact that multiple genetic changes are required to produce a cancer cell helps explain the predispositions to cancer that run in families. ○ An individual inheriting an oncogene or a mutant allele of a tumor-suppressor gene is one step closer to accumulating the necessary mutations for cancer to develop. • Geneticists are devoting much effort to finding inherited cancer alleles so that a predisposition to certain cancers can be detected early in life. • About 15% of colorectal cancers involve inherited mutations. • Many of these mutations affect the tumor-suppressor gene adenomatous polyposis coli or APC. ○ Normal functions of the APC gene include regulation of cell migration and adhesion. ○ Even in patients with no family history of the disease, APC is mutated in about 60% of colorectal cancers. • Between 5% and 10% of breast cancer cases show an inherited predisposition. ○ Breast cancer is the second most common type of cancer in the United States, annually striking more than 180,000 women and leading to 40,000 deaths. • Mutations in one gene, BRCA1, increase the risk of breast and ovarian cancer. ○ Mutations in BRCA1 and the related gene BRCA2 are found in at least half of inherited breast cancers. • A woman who inherits one mutant BRCA1 allele has a 60% probability of developing breast cancer before age 50 (versus a 2% probability in an individual with two normal alleles). ○ Both BRCA1 and BRCA2 are considered tumor-suppressor genes because their wild-type alleles protect against breast cancer and their mutant alleles are recessive. • BRCA1 and BRCA2 proteins function in the cell’s DNA damage repair pathway. ○ BRCA2, in association with another protein, helps repair breaks that occur in both strands of DNA. • Because DNA breakage can contribute to cancer, the risk of cancer can be lowered by minimizing exposure to DNA-damaging agents, such as ultraviolet radiation in sunlight and the chemicals found in cigarette smoke. • In addition to mutations and other genetic alterations, a number of tumor viruses can cause cancer in various animals, including humans. ○ In 1911, Peyton Rous, an American pathologist, discovered a virus that causes cancer in chickens. ○ The Epstein-Barr virus, which causes infectious mononucleosis, has been linked to several types of cancer in humans, notably Burkitt’s lymphoma. ○ Papillomaviruses are associated with cancer of the cervix, and a virus called HTLV-1 causes a type of adult leukemia. • Worldwide, viruses seem to play a role in about 15% of the cases of human cancer. • Viruses can interfere with gene regulation in several ways if they integrate their genetic material into a cell’s DNA. ○ Viral integration may donate an oncogene to the cell, disrupt a tumor-suppressor gene, or convert a proto-oncogene to an oncogene. ○ Some viruses produce proteins that inactivate p53 and other tumor-suppressor proteins, making the cell more likely to become cancerous. Lecture Outline for Reece et al., Campbell Biology, 10th Edition, Copyright © 2014 Pearson Education, Inc

(28) MTH1.1: Understanding Similar and Congruent Triangles

Geometry: Diliations and similarity

PA seminar

Prosthetic Alignment & Pressure Terms Seminar and Crossword

6 mark - explain the similarities / differences between....

Карточки Тема 16: Similarities (Сходства) | Quizlet

NURS 2866 - Week 1 Seminar Packet

Seminar 5-6 - Trial by Jury, When the Public are the Judges

Seminar 7 - Jurisprudence

Seminar 3 - moving beyond judges' policy preferences

Senior Seminar Vocab 50-100

Similarity and Difference Between Two Pictures

Seminar 4 - ASM (artisanal and small-scale miners) - Business and Human Rights Tort

Senior Seminar Exam 3

Gustar and Similar Verbs(only infinitives)

Special Seminar 2 - Business and Human Rights Tort

Special Seminar 1 - Business and Human Rights Tort

NURS 2866 - Week 2 Seminar

Vascular Structures The circulatory system comprises blood vessels responsible for transporting blood throughout the body. The vascular structures are categorized into three types: arteries, veins, and capillaries. Understanding their functions and differences is crucial for patient care technicians. Arteries Arteries are blood vessels that carry freshly oxygenated blood from the heart to the various tissues and organs in the body. These vessels have thick walls to withstand the high pressure generated by the heart. Key Arteries to Know: * Coronary Artery: Supplies blood to the heart muscle itself. * Femoral Artery: Located in the thigh, supplying blood to the lower limbs. * Pulmonary Artery: Carries deoxygenated blood from the heart to the lungs for oxygenation. Veins Veins are blood vessels that carry deoxygenated blood from the body back to the heart. Unlike arteries, veins have thinner walls and contain valves that prevent the backflow of blood. Key Veins to Know: * Jugular Vein: Located in the neck, returns blood from the head and neck to the heart. * Saphenous Vein: A large vein running along the leg, important in procedures like varicose vein treatment. * Pulmonary Vein: Carries oxygenated blood from the lungs back to the heart. Capillaries Capillaries are the smallest blood vessels and serve as the site for nutrient, gas, and waste exchange between the blood and body cells. They are extremely permeable, allowing oxygen and nutrients to move into cells and carbon dioxide and waste products to move out. * Function: Capillaries allow the exchange of gases, nutrients, and waste products with surrounding tissues. The thin walls facilitate this process, and they play a crucial role in maintaining homeostasis. Infection Control Practices As a Patient Care Technician, it is essential to practice infection control techniques to prevent the transmission of infectious agents during patient care. This is especially critical when performing invasive procedures. Personal Protective Equipment (PPE) PPE protects both healthcare workers and patients from potential infections. Common PPE includes gloves, gowns, masks, face shields, and goggles. * Always wear appropriate PPE based on the procedure and the patient's condition. * Hand Hygiene: Wash hands thoroughly before and after patient contact and before performing procedures. Always use hand sanitizer if soap and water are unavailable. * Safe Disposal: Dispose of equipment like needles and gloves properly to prevent the spread of infection. Dispose of sharps in a sharps container immediately after use. Preventing Infection During Invasive Procedures When performing procedures such as blood draws, catheter insertions, or injections, ensure the environment is sterile. Follow these guidelines: * Sterile Technique: Ensure that all equipment is sterile before use and that the procedure area is clean. * Use of Clean Materials: Always check that materials such as gauze pads, alcohol wipes, and bandages are intact and not expired. Patient Identification and Consent Patient identification and consent are vital aspects of delivering safe care. Patient Identification To prevent errors, always verify patient identity before conducting any procedure. Use two acceptable patient identifiers (e.g., name, date of birth, medical record number). * Verification Process: 1. Confirm patient’s identity by asking for their name and date of birth. 2. Compare the patient's provided information with the information on the requisition form. Consent Before any procedure, obtain verbal or written consent from the patient. Always confirm the patient understands the procedure and consents voluntarily. Patients have the right to refuse consent for any reason, whether personal, cultural, or medical. * If a patient refuses consent, document the refusal and notify the nurse or supervising healthcare professional immediately. Handling and Safety of Medical Equipment Proper handling and safety protocols for medical equipment are critical in patient care. Always inspect equipment thoroughly to ensure its functionality and safety. Needles and Syringes * Inspection: Visually inspect needles for any burrs, bends, or defects before and after removing the cap. * Single Use Only: Needles should only be used once, even if it is for the same patient. * Deploy Safety Devices: Immediately activate the safety device after use to protect yourself and others. Place used needles in a sharps container as soon as possible. Evacuated Tubes Evacuated tubes are used for blood collection, and their integrity is crucial for obtaining accurate test results. * Expiration Dates: Always check the expiration date on the tube packaging before use. Expired tubes may not function properly. * Inspect for Cracks or Breaks: Do not use tubes with cracks, breaks, or missing labels. * Additives: Ensure that the additives in the tubes are not expired as expired additives can alter test results. * Do Not Use Without Labels: Ensure that the tubes are correctly labeled with the patient's information. Tourniquets Tourniquets are used to temporarily restrict blood flow during venipuncture. Inspect the tourniquet before use. * Inspection: Ensure the tourniquet is free of tears, rips, dirt, or contamination. * Single Use vs. Multiple Use: Some tourniquets are disposable while others are reusable. Always clean reusable tourniquets between uses. Specimen Collection and Labeling Accurate labeling and handling of specimens are crucial for diagnostic accuracy. Labeling Specimens * Label Before Leaving the Room: Always label specimens in front of the patient to ensure proper identification. * Required Information: Labels must include the patient’s full name, date of birth, date and time of collection, and the medical or facility identification number. * Placement of Labels: Place the label over the preprinted label and ensure that the stopper is not covered. Be careful to avoid creases or wrinkles on the label. * Do Not Allow Others to Label: Never allow someone else to label your specimens, and do not label for others. Handling of Requisition Forms * Verification: Always verify that the requisition form matches the patient’s information and the test ordered. * Documentation: Ensure that any discrepancies are resolved before proceeding with specimen collection. Key Points * Vascular structures: arteries (e.g., coronary, femoral, pulmonary), veins (e.g., jugular, saphenous, pulmonary), and capillaries are essential for circulatory functions. * Infection control is vital in all patient care tasks, including the use of PPE, hand hygiene, and safe disposal of contaminated materials. * Always confirm the patient’s identity and obtain consent before performing procedures. * Inspect needles, tubes, and tourniquets for defects to ensure patient safety. * Properly label and handle specimens to prevent errors and ensure accurate test results. Dermal Punctures Dermal punctures are blood collection procedures that involve the puncturing of the skin’s surface to collect a smaller amount of blood, typically for diagnostic purposes. This method is commonly used when only a small sample is required or when venous access is difficult. * Alternative Names: Dermal punctures are sometimes called heel sticks, finger sticks, or capillary puncturesdepending on the patient’s age and the area from which blood is drawn. * Comparison with Venipuncture: Dermal punctures remove smaller amounts of blood compared to venipuncture, which involves drawing blood from veins. Dermal punctures are less invasive and are typically used when only a small sample is needed for testing. Indications for Dermal Puncture Dermal punctures are useful in various clinical scenarios. It’s essential to understand when and why dermal punctures are preferred over other methods of blood collection: * Small Amounts of Blood: Dermal punctures are used when only a small amount of blood is required, such as for point-of-care tests like glucose monitoring, cholesterol checks, and hematocrit levels. * Inaccessible Veins: In cases where veins are not easily accessible, such as with infants, elderly patients, or patients with specific medical conditions, dermal punctures provide an alternative solution. * Capillary Blood Required: Some laboratory tests require capillary bloodbecause it offers a mix of arterial, venous, and capillary blood, which can provide different insights into a patient’s health. * Risk of Iatrogenic Anemia: Dermal punctures are also preferred in cases where multiple blood draws could lead to iatrogenic anemia, particularly in infants, as they have a smaller blood volume and are more at risk of developing anemia from repeated venipunctures. * Common Uses for Point-of-Care (POC) Tests: Dermal punctures are often used for point-of-care tests (POC), which are rapid tests performed at or near the site of patient care. Common POC tests include: * Glucose: Blood sugar testing for diabetes management. * Cholesterol: Monitoring cholesterol levels to assess cardiovascular health. * Hematocrit: Assessing the percentage of red blood cells in blood. Dermal Puncture in Infants and Children Dermal punctures are commonly performed on infants younger than 1 year old due to the following reasons: * Less Blood Required: Infants require much smaller blood samples, and dermal punctures provide an easy way to collect blood without the need for large quantities. * Avoiding Damage to Blood Vessels: Repeated venipuncture in infants can damage their fragile veins and blood vessels. Dermal punctures reduce this risk and provide an effective alternative. * Preferred Sites for Infants: Heel sticks are the most common method used for infants, and the preferred sites are the medial or lateral sides of the plantar surface of the heel. Blood Composition in Dermal Punctures When performing dermal punctures, it’s important to understand the composition of the blood being collected. Dermal puncture blood specimens contain three types of blood: * Arterial Blood: Blood that is rich in oxygen and comes from the arteries. * Capillary Blood: Blood that comes from the capillaries and reflects a mixture of arterial and venous blood. * Venous Blood: Blood that is deoxygenated and returns to the heart from the body. Important Note: Because dermal punctures involve a mix of these three types of blood, it’s essential to document on the requisition form that a dermal puncture was performed, as the composition differs from that of venous blood, which may affect test results. Performing Dermal Punctures on Adults and Children For adults and children older than one year, finger sticks are commonly performed. Below are detailed instructions on how to perform a finger stick correctly: Finger Stick * Preferred Site: Perform the finger stick on the third or fourth finger of the patient’s non-dominant hand. * Site Selection: Choose the fleshy, off-center side of the finger to avoid nerves and bones. * Avoid Certain Fingers: Never perform finger sticks on fingers that are: * Cold * Cyanotic (bluish discoloration) * Scarred * Swollen * Rash-covered * Wipe the First Drop: After making the puncture, wipe away the first drop of blood because it may contain tissue fluid or contaminants that could affect test results. * Collect the Second Drop: Use the second drop of blood for the collection to ensure a clean sample. * Lancet Insertion: Insert the lancet at a 90-degree angle (perpendicular to the fingerprint) to ensure the proper depth of puncture. Heel Stick (For Infants) * Preferred Site for Heel Stick: The medial or lateral sides of the plantar surface of the heel are the best sites for performing a heel stick. Avoid the back of the heel because it may damage sensitive structures. * Warm the Heel: Apply a heel warmerfor 3 to 5 minutes before performing the procedure. This helps to increase blood flow to the area and makes the blood easier to collect. * Wipe the First Drop: Similar to finger sticks, wipe away the first drop of blood to ensure accurate collection from the second drop. Key Points * Dermal punctures are ideal when a small sample of blood is needed, when venous access is difficult, or when point-of-care tests are required. * For infants and children under 1 year, dermal punctures, especially heel sticks, are the best option due to the limited blood volume and the risk of damaging their veins. * Finger sticks for adults and children over 1 year old should be performed on the third or fourth finger of the non-dominant hand. * Lancet insertion should be done at a 90-degree angle to the fingerprint. * Always wipe away the first drop of blood to avoid contamination and collect the second drop for the test. * For heel sticks, apply a heel warmer for 3 to 5 minutes to improve blood circulation in the infant’s foot. Safety and Comfort During Blood Collection * The primary goals during blood collection are to ensure patient safety, provide comfort, and obtain specimens efficiently and effectively.  Patient Positioning * Never perform venipunctures with patients standing or sitting on a high stool or the edge of an examination table. * The optimal position for venipuncture is for the arm to be fully extended with the palm facing upward. Venipuncture Site Selection * Begin by palpating the veins in the antecubital area. * First Choice: Median cubital vein (preferred due to its size and location). * Second Choice: Cephalic vein (often accessible and fatty). * Third Choice: Dorsal hand vein (smaller and less ideal). * Last Choice: Basilic vein (close to the radial nerve and brachial artery, making it riskier to puncture). * The ideal vein for venipuncture should be well anchored, feel spongy and bouncy, and should be straight and easy to access with a needle. Special Considerations * Avoid collecting blood from the arm on the affected side of a patient who has had a mastectomy. * Do not perform collections in any area with tattoos, as this can influence results. * Avoid collecting blood through a hematoma, as it can alter results and cause pain. * Steer clear of areas with edema, as collection may yield excess fluid and discomfort for the patient. * Do not collect blood from scarred areas, as access may be difficult and painful. * Avoid sclerotic veins, as blood flow may be inadequate, making collection painful. Tourniquet Application * Apply a tourniquet 3 to 4 inches above the antecubital area or above the wrist bone. * The tourniquet must be removed within one minute of application to prevent hemoconcentration. Preparation for Venipuncture * Allow the alcohol to dry completely before performing venipuncture; do not fan or blow on it to speed up the drying process. * Insert the needle until you feel a change in resistance (indicating entry into the vein). Stop insertion once this is felt. Blood Collection Techniques * The most common method for venipuncture is the evacuated tube system. * Equipment needed includes: * Gloves * Isopropyl alcohol swabs or pads * Gauze pads * Tape * Self-adhesive wrap or adhesive bandages * Tourniquet * Needles * Hub adapter or needle holder * Blood collection tubes * Always check tubes for additives, expiration dates, and the amount of blood they can hold. * Common additives are anticoagulants or clot activators. Angles for Needle Insertion * For antecubital area: Insert the needle at a 15 to 30-degree angle. * For hand collection: Insert the needle at a 10-degree angle. Special Collection Devices * Winged Infusion Devices: Used for patients with small or difficult veins, primarily on the dorsal hand vein. * Syringe Method: Utilized for patients with fragile veins that can easily collapse; this method allows for controlled and adjustable blood withdrawal, minimizing the risk of vein collapse. Importance of Urine Specimens * One of the most commonly performed diagnostic tests involves urine specimens. * Urinalysis includes examining: * Appearance * Color * Odor * pH * Specific gravity * Presence or absence of protein, glucose, or hemoglobin. Urine Culture * Urine culture tests are performed for the growth and identification of microorganisms. Types of Urine Specimen Collections: * Random Collection: * The most common urine test. * Can be done at any time without restrictions or preparations. * First Morning Urine Specimen: * Instruct the patient to urinate before going to bed. * Collect the first urination when they wake up. * Timed Urine Specimen: * Provide a rigid, light-resistant container with a capacity of about 3000 mL and a wide-mouth, leak-proof screw-on cap. * 24-Hour Collection: * The patient begins at a specific time and collects all urine until the same time the next day. * If a patient forgets or discards any urine, they must start the process over. Specialized Urine Tests: * Glucose Tolerance Test: * Requires fasting for a specific duration. * Typically collected at the same time as a blood collection and done every 1 to 2 hours. * Postprandial Test: * Patient urinated, then eats a meal. * Collect a urine sample 2 hours after eating. * Clean Catch Midstream: * Patient should urinate a little, stop, and then collect the sample before completing urination. * Important Note: Never use alcohol, hydrogen peroxide, or iodine to clean the genitals prior to collection. Reagent Strips and Urinalysis Results * Reagent strips provide information about: * pH * Specific gravity * White blood cells * Hemoglobin * Ketones * Bilirubin * Glucose. * Expected Ranges: * pH: 4.6-8.0 (ideal around 6.0). * Specific gravity: 1.005-1.030 (typically around 1.010-1.025). Other Types of Specimens: * Saliva Specimens: Used for hormone, alcohol, and drug levels. * Sputum Samples: * Mucus and secretions from the lungs and trachea. * Should be collected first thing in the morning before brushing teeth or eating/drinking. * A sample should be about 1 to 2 teaspoons. * Fecal Specimens: Used to test for bacterial infections, parasites, or occult blood. Ensure urine is not present in the fecal sample. * Semen Specimens: * Used for sperm counts, fertility assistance, and identity proof in rape cases. * Keep samples warm and protect them from light. * Throat Swabs: Culture specimens that help identify strep throat. * Wipe both tonsils, the throat, and any inflamed/infected areas. * Buccal Swab: Swabs the inside of the cheek to collect the patient’s DNA. Introduction to Blood Cultures Blood cultures are laboratory tests designed to detect bacteria or other microorganismspresent in the bloodstream. The primary goal of this test is to identify infections caused by bacteria or fungi, which can lead to serious health complications if not treated promptly. Purpose of Blood Cultures Blood cultures are used to: * Diagnose Infections: Providers request blood cultures when they suspect that a patient has a bloodstream infection, which could be caused by bacteria, fungi, or other pathogens. This helps doctors determine the exact cause of the infection so they can select the appropriate treatment (e.g., antibiotics or antifungals). * Identify the Causative Microorganisms: Blood cultures allow laboratories to grow and identify microorganisms from the patient’s blood, which can be critical in diagnosing conditions like sepsis, endocarditis, or infections originating from other parts of the body. How Blood Cultures Work 1. Specimen Collection: Blood is drawn from the patient’s vein. The sample is then placed into specialized blood culture bottles. 2. Incubation: The blood is cultured in a laboratory, meaning it is placed in dishes or bottles containing a growth medium. This medium promotes the growth of microorganisms present in the blood. 3. Observation: The blood culture bottles are observed over a period of time to see if any microorganisms begin to grow. This growth indicates the presence of an infection-causing microorganism. 4. Identification: Once growth is detected, laboratory technicians further analyze the sample to identify the specific microorganism. This allows them to determine what type of infection the patient has, which informs treatment decisions. Collection of Blood Cultures When collecting blood for culture, it is essential to follow proper procedures to ensure that the sample is accurate and uncontaminated. Site Selection and Preparation The site of collection plays a crucial role in obtaining a quality blood culture sample. Contamination can lead to inaccurate results, so it is essential to follow proper protocols for disinfecting the collection site. * Disinfection of the Collection Site: To prevent contamination from skin microorganisms, the collection site must be disinfected thoroughly before drawing blood. Follow your facility’s guidelines, but generally, the site should be cleaned for 30 to 60 seconds. * Disinfecting Procedure: 1. Use an alcohol-based antiseptic(e.g., chlorhexidine or iodine) to clean the site. 2. Scrub the area in a circular motionstarting from the center and working outward. 3. Allow the disinfectant to air dry to ensure its effectiveness. * Proper Technique: Always disinfect the site just before collecting the blood culture to avoid introducing any microorganisms that may be present on the skin. Blood Culture Bottles You will need to use two bottles for each blood culture collection: one for aerobic bacteria (which need oxygen to grow) and one for anaerobic bacteria (which grow in the absence of oxygen). * Aerobic Bottle: This bottle contains a growth medium that supports the growth of microorganisms that require oxygen. It is used for collecting blood samples that may contain aerobic bacteria. * Anaerobic Bottle: This bottle supports the growth of bacteria that thrive without oxygen. It is essential for collecting samples that may contain anaerobic bacteria. Both bottles are typically marked with color codes or labels indicating which type of microorganism they are designed to cultivate. Blood Volume and Timing * Amount of Blood: A set of blood cultures typically requires a specific volume of blood to be collected. This ensures that enough material is present for the laboratory to perform the necessary tests. Always follow the instructions from the lab or facility for the required volume. * Multiple Sets: In some cases, multiple sets of blood cultures may be needed for accurate diagnosis, especially in cases of suspected sepsis or other severe infections. * Timing: Blood cultures should be collected before starting antibiotics, as antibiotics can kill the microorganisms in the blood and interfere with the culture results. If antibiotics are already being administered, notify the laboratory, as this can affect the accuracy of the results. Guidelines for Blood Culture Collection Labeling and Documentation * Accurate Labeling: Label the blood culture bottles with patient identifiers, such as the patient’s name, date of birth, and medical record number, to avoid mix-ups. * Documenting the Collection: Always document the following information on the requisition form: * The site from which the blood was collected. * The time of collection. * The collection method (whether it was an aerobic or anaerobic sample). * Notify the Laboratory: If there are any unusual circumstances (such as suspected contamination), make sure to notify the laboratory so they can take appropriate precautions when handling the sample. Special Considerations Blood cultures are a critical diagnostic tool, and as a Patient Care Technician, it is important to understand the procedures and the potential consequences of improper collection. Infection Prevention * Always use sterile equipment and maintain a clean technique throughout the blood culture collection process. * Wear gloves and follow standard infection control protocols, including wearing appropriate PPE (personal protective equipment) to protect both yourself and the patient from cross-contamination. Handling and Transporting Blood Cultures * After collection, make sure to transportthe blood culture samples to the laboratory as soon as possible. * Avoid delays in transporting blood cultures to the lab, as prolonged exposure to room temperature can affect the growth of microorganisms. * Follow your facility’s guidelines for sample transport to ensure that the blood culture samples reach the laboratory in optimal condition. Key Points * Blood cultures are used to detect microorganisms (e.g., bacteria, fungi) in the blood and are critical in diagnosing infections such as sepsis and endocarditis. * Proper site disinfection (30-60 seconds) before collection is essential to avoid contamination and ensure accurate results. * Always collect one set of blood culture bottles per collection: one for aerobicand one for anaerobic microorganisms. * Multiple sets may be required, and blood cultures should be collected before administering antibiotics for the most accurate results. * Accurate labeling and documentationare vital to ensure proper identification and handling of specimens. * Handle and transport blood culture samples promptly and follow infection control protocols to maintain a sterile environment. Phlebotomy Overview Phlebotomy is the process of obtaining a blood sample from a patient, usually through a venipuncture (insertion of a needle into a vein). This is a common procedure performed in medical settings, and as a PCT, you may be asked to assist with or directly perform this task. The following is a breakdown of important steps and safety protocols: * Preparation: Ensure you have all necessary equipment, including gloves, gauze, alcohol swabs, bandages, and blood collection tubes. * Patient Identification: Always confirm the patient's identity to ensure correct specimen collection. * Technique: Be aware of the anatomy and correct venipuncture sites, including the antecubital fossa (area inside the elbow) and dorsal veins on the hand. Pressure on the Puncture Site After collecting the blood sample, it is criticalto apply appropriate pressure to the puncture site to stop the bleeding and prevent hematoma formation. A hematoma is a localized collection of blood under the skin, which can happen if both walls of the blood vessel are pierced during a venipuncture. * Pressure Application: Make sure to hold pressure on the puncture site for several minutes to stop the bleeding. Ensure the patient maintains the pressure to minimize the risk of bruising. * Bandage Application: Once the bleeding has stopped, a bandage should be placed on the puncture site. Observing for Complications Following a venipuncture, it is essential to monitor the patient for any complications that may arise. While most procedures are safe, complications can occur, and early identification is crucial for the patient's safety. Monitor the patient for the following complications: * Color Changes: Observe for any changes in the patient’s skin color, particularly signs of paleness or discoloration. * Diaphoresis: Excessive sweating could indicate nausea, syncope, or a panic attack. * Dyspnea or Shortness of Breath: This could signal respiratory distress and must be reported immediately. * Confusion: A change in mental status can indicate complications like shock or hypoxia. Complications of Phlebotomy It is important to understand the various complications that can arise during phlebotomy procedures. Some of these may be minor, while others could indicate more serious issues. Below is a comprehensive list of potential complications you may encounter: 1. Nerve Damage * Although rare, nerve damage can occur during venipuncture. The patient may report a sensation of numbness or a pin-and-needles feeling at the puncture site. If the patient experiences these symptoms, it is important to stop the procedure immediately and inform the nurse or supervisor. 2. Hematoma * A hematoma is a common complication, resulting from the rupture of the blood vessel wall during venipuncture. It is characterized by a localized blood collection under the skin. To minimize hematoma formation, ensure you apply adequate pressure to the puncture site after the procedure. 3. Infection * Infection is a risk with any invasive procedure, although it is rare in venipuncture. It is important to follow sterile procedures to reduce the likelihood of infection. If an infection develops, it may present as redness, swelling, or warmth around the puncture site. 4. Phlebitis * Phlebitis is inflammation of the vein, often caused by repeated use of the same vein. It may present with signs of warmth, tenderness, and redness around the puncture site. This condition is uncommon but requires attention to prevent further damage to the vein. 5. Petechiae * Petechiae are small red or purple spots on the skin. They can occur due to the rupture of small blood vessels under the skin. Though unpleasant and upsetting for the patient, petechiae are generally not dangerous and will resolve on their own. 6. Thrombus (Blood Clot) * A thrombus or blood clot can form if adequate pressure is not applied to the venipuncture site. It is essential to ensure that the patient applies sufficient pressure after the procedure to prevent clot formation. Other Reactions and Symptoms While performing venipuncture, it is important to be aware of the following minor to severe reactions that may occur: * Dizziness * A common minor physical reaction, dizziness usually resolves without treatment within a few minutes. Encourage the patient to rest and monitor for any additional symptoms. * Syncope (Fainting) * Syncope is uncommon but can occur during a venipuncture, especially in patients who are anxious. In rare cases, the patient may fall or suffer a more serious complication like an arrhythmia or stroke during the syncopal episode. * If a patient experiences syncope, lay them down and elevate their legs. Call for help immediately and stay with the patient until assistance arrives. * Nausea * If a patient feels nauseated before the blood collection, wait a few minutes before proceeding. Ensure the patient is not left alone. Use a cold compress on the patient's head or the back of their neck, provide a wet cloth to clean their mouth, and offer a glass of water if the patient vomits. Inform the nurse of the situation. * Diaphoresis (Excessive Sweating) * Excessive sweating can signal nausea, syncope, or a panic attack. Ask the patient how they are feeling, provide a tissue or towel, and ensure the patient is not left alone. Observe the patient for any further signs of complications and notify the nurse immediately. * Seizure * If the patient has a seizure during the procedure, stop the procedure immediately and seek emergency assistance. Do not attempt to restrain the patient. Remove any objects from the area that could harm the patient and stay with them, providing as much privacy as possible. * Shock * Symptoms of shock include cold, clammy, and pale skin, rapid pulse, increased shallow breathing, and a blank stare. If you suspect shock, call for help immediately. Ensure the patient has an open airway and, if they are laying down, lower their head below the body. Keep the patient warm and safe until help arrives. Key Points * As a PCT, your primary responsibility is to ensure patient safety and comfort during venipuncture. Always monitor for complications and be ready to take action if any adverse reactions occur. * Familiarize yourself with the common complications and learn how to handle them appropriately. Remember, your role may not involve diagnosing or treating these complications, but you are responsible for reporting any signs of trouble to your supervisor or healthcare provider. * Effective communication with the healthcare team is crucial. If you notice something unusual during the procedure, always report it immediately to the appropriate person. Importance of Specimen Handling, Packaging, and Communication The delivery process of laboratory specimens must be precise to ensure the accuracy of test results. Every step in the specimen handling process plays a significant role in maintaining the quality of the sample and in complying with established protocols. * Adequate Specimen Handling: Specimens should be handled with care to avoid contamination, degradation, or incorrect results. Proper techniques ensure that the samples remain intact and viable for testing. * Packaging and Communication: Proper packaging is critical to prevent spillage, contamination, or loss during transport. The communication of specimen details (e.g., patient ID, collection time, and test type) ensures that laboratory personnel can accurately process the sample. Always label specimens immediately after collection. Temperature-Specific Specimen Handling Certain tests require that specimens are maintained at specific temperatures to preserve their integrity until they reach the laboratory. * Heat Sources and Ice Slurries: Specimens that require specific temperature handling should be kept in appropriate temperature conditions immediately after collection. Common temperature controls include: * Heat Block or Heat Source for maintaining warmth. * Ice Slurry or Refrigerator/Freezer for cold storage. * Some tests require specific temperature handling as detailed below: * Ammonia and Lactic Acid: These blood samples must be placed in an ice slurry immediately after collection to maintain their stability. * Cold Agglutinins: These samples should remain at body temperature (37°C) during transport and testing to prevent interference with test results. * Bilirubin and Folate Levels: To protect blood samples from light, wrap the collection tube in foil to prevent degradation due to photosensitivity. * Blood Gas Tests: For these tests, store specimens at room temperature for 15 to 30 minutesor in an ice slurry for up to 1 hour. * Coagulation Tests: Analysis should be performed within 1 hour of specimen collection to ensure accurate results. * Photosensitive Specimens: Always protect specimens that are photosensitive, such as those for bilirubin or folate, from light to avoid changes in their composition. Timed Tests and Proper Labeling Timed Tests: Ensure the patient has fulfilled the necessary requirements for the test timing. Timed tests are critical for conditions where the concentration of the substance being tested varies over time (e.g., glucose, cortisol, etc.). * Labeling of Specimens: Label every collection container immediately after collection to prevent errors: * Patient's full name and identification number * Date and time of collection * Specimen type * Clear labeling ensures that the sample can be accurately tracked, preventing mix-ups or delays in processing. Urine Specimen Handling Urine specimens are often collected for analysis and must be handled with specific care to ensure accurate results. * Glove Use: Always wear gloves when handling patient-collected nonblood specimens to reduce the risk of contamination. Change gloves between handling each specimen to prevent cross-contamination. * Refrigeration: If a urine specimen is not going to be tested immediately, it should be refrigerated to preserve its composition and prevent bacterial growth. The specimen should be delivered to the laboratory within 1 hour of collection. * Room Temperature for Certain Tests: Some urine tests are best performed at room temperature, so verify whether immediate refrigeration is necessary. * Transferring Specimens: To transfer urine from a collection container to a transport container, use a disposable pipette or carefully pour the urine into the tube after removing the stopper. Always avoid contamination when transferring the sample. * Preserved Urine Specimens: For urine specimens that have been preserved with chemicals, keep the tubes at room temperature for no longer than 72 hours before performing a urinalysiswith chemical reagent strip testing. * Culture and Sensitivity Tests: Specimens for culture and sensitivity testing should also be kept at room temperature for up to 72 hours before analysis. Specimen Delivery Methods When specimens are ready for transport, they must be delivered to the laboratory using safe and efficient methods to prevent degradation or contamination. * Plastic Biohazard Bags: Always place specimens in biohazard bags with zipper seals to prevent spillage and to clearly communicate that the contents are biologically hazardous. Ensure that the specimen is adequately secured before transport. * Hand Delivery: In some cases, specimens may need to be delivered directly to a reference laboratory. When hand-delivering specimens: * Follow the timeliness of delivery guidelines. * Complete necessary log-in processes to track the sample's arrival. * Use proper carrying devices (e.g., coolers, bags) to prevent damage during transport. * Pneumatic Tube Systems: Commonly used in inpatient settings, pneumatic tube systems offer enhanced mechanical reliability and increased transport distance and speed. These systems also feature specific control mechanisms and shock-absorbing features to prevent hemolysis (destruction of red blood cells) during blood specimen transport. * Automated Carrier Systems: Automated transport systems use motorized containers and share many of the same features as pneumatic tube systems. These systems help streamline the transport process while maintaining the integrity of the specimens. Introduction to the Clinical Laboratory Improvement Act (CLIA) The Clinical Laboratory Improvement Act (CLIA) is a U.S. federal law that was passed in 1988. The purpose of CLIA is to regulate laboratory testing to ensure that patients receive accurate and reliable test results. CLIA sets specific standards for laboratories performing tests on specimens collected from humans, ensuring that patient care meets safety and accuracy standards. As a Patient Care Technician (PCT), you will be responsible for performing certain laboratory tests that fall under CLIA-waived procedures. These are tests that the CLIAdeems to carry a low risk for patient harm, often due to the simplicity of the procedure and the type of specimens involved. These tests are common in both medical facilities and patients' homes. CLIA-Waived Procedures CLIA-waived tests are defined as those that: * Present a minimal risk to the patient. * Involve small amounts of blood or easily collectable specimens (such as urine). * Are simple and easy to perform, which reduces the potential for error and harm. These tests include commonly performed procedures such as: * Urine dipstick tests * Glucometer tests * Pregnancy tests * Hemoglobin A1C tests Key Responsibilities in CLIA-Waived Testing When performing CLIA-waived tests, there are specific procedures you must follow to ensure the accuracy and safety of the test. Below is an outline of the key responsibilities you have when performing these tests. Confirming Written Test Requests Before performing any test, confirm that you have received a written test request from the healthcare provider. This request ensures that the test being performed is necessary and appropriate for the patient's care. Establishing Patient Identification Accurate patient identification is crucial. Always verify that the patient is the correct individual by using at least two unique identifiers, such as their full name and date of birth, before collecting any specimen. Providing Pretest Instructions Some tests require specific instructions for the patient to follow before the test. It is your responsibility to provide the patient with clear pretest instructions and ensure that the patient understands and follows them. Afterward, verify with the patient that they followed the instructions correctly. Collecting Specimens Specimens should be collected according to the package insert instructions provided with the test kit. Always make sure you are using the correct specimen collection method and tools for the test. Pay attention to the recommended procedure to avoid sample contamination. Labeling Specimens Accurately Accurate labeling of specimens is essential to prevent misidentification and errors. Label specimens immediately after collection with the patient's name, identification number, date and time of collection, and specimen type. Avoiding Expired Reagents or Test Kits Using expired reagents or test kits can lead to inaccurate results. Always check the expiration date on the test kits and reagents before use. Never use any kit or reagent that has passed its expiration date. Performing Quality Control Testing Before performing patient tests, you must perform quality control testing using the control solutions provided in the test kit. Quality control tests ensure that the testing equipment and reagents are working correctly. * Correcting Problems: If a problem is discovered during the quality control testing, resolve it before testing patient samples. If the control results are not within the acceptable range, investigate the issue, and perform corrective actions. * Frequency of Quality Control Testing: Your facility should have policies in place for the frequency of quality control testing. Follow these policies to ensure consistent accuracy in testing. Test Timing Recommendations Each test has specific timing guidelines that must be followed carefully. The timing recommendations are typically included in the package insert for the test. Follow the instructions to ensure that the test is performed accurately. Interpreting Test Results After performing the test, interpret the results by referring to the package insert information. Always be aware of the normal ranges and the specific steps to interpret the results. Recording and Reporting Test Results Once you interpret the test results, it is your responsibility to record them accurately and report them to the healthcare provider in a timely manner. Ensure that you document the results clearly and communicate any abnormal findings immediately. Follow-up or Confirmatory Testing If a test result indicates the need for follow-up or confirmatory testing, make sure to follow the package insert recommendations. You may need to communicate with the healthcare provider to discuss next steps. OSHA Regulations and Biohazardous Waste Disposal When performing any medical testing, it is essential to follow OSHA regulations for the safe disposal of biohazardous waste. This includes disposing of used test strips, gloves, and other materials in appropriate biohazard containers to minimize the risk of contamination or infection. * Biohazardous Waste Disposal: All materials that come into contact with blood, urine, or other bodily fluids should be disposed of in red biohazard bags or sharps containers as appropriate. Always follow your facility's protocol for waste disposal. Participation in Quality Assurance Programs You are responsible for participating in quality assurance and quality assessment programs for every test you perform. These programs are designed to ensure that testing is done accurately and that standards are continuously met. * Reviewing Performance: You will regularly review test results, quality control data, and procedures to assess whether improvements are needed. * Corrective Actions: If quality issues arise, corrective actions should be implemented promptly to ensure that the testing process remains reliable and safe. Glucometer Test Controls One of the most common CLIA-waived tests you will perform is blood glucose testing using a glucometer. For accurate results, you must always follow the correct procedures when performing these tests. Performing Liquid Controls * Liquid controls should be used every time you open a new package of glucometer test strips. * Use liquid controls at room temperature and ensure they are within the expiration date. Logging Test Control Results * Log the time and date of control testing, as well as the serial number of the glucometer you used. This will ensure traceability and consistency in testing. Proper Storage of Test Strips * Store glucometer test strips at room temperature and close the packageafter each use to keep the strips dry. * Ensure that test strips are not exposed to extreme temperature changes or moisture. Cleaning the Glucometer * After each use, clean the glucometerwith an alcohol wipe to remove any contamination and maintain the accuracy of the device. Preanalytical Errors Preanalytical errors are mistakes that occur before the analysis of a specimen in the laboratory. These errors can lead to inaccurate test results and affect patient care. As a PCT, your responsibility is to minimize these errors by following best practices during specimen collection and handling. Preanalytical errors can occur in several stages, including: * Specimen collection (e.g., improper technique, wrong site) * Specimen handling (e.g., incorrect transportation, improper mixing) * Specimen labeling (e.g., incorrect or missing patient information) By ensuring proper technique and avoiding common mistakes during the preanalytical phase, you can help ensure accurate and reliable test results. Factors Affecting Specimen Collection Several physiological and environmental factors can affect specimen collection. Understanding these factors helps minimize preanalytical errors: Veins and Skin Conditions * Sclerotic veins (hardened veins) and scarred skin can make venipuncture more difficult. If the veins are sclerotic or the skin is scarred, always find another site to collect the specimen. Stress * Stress can cause physiological changes, such as an elevation in white blood cells, decreased iron levels, and abnormal hormone levels, which may affect test results. Ensure the patient is relaxed before drawing blood whenever possible. Other Considerations * Menstrual cycle: Blood tests may be affected by a patient's menstrual cycle, potentially altering results such as hormone levels. * Edema: Swelling or edema in the arms can make it difficult to find veins and may affect the specimen. * Medications: Certain medications can influence test results, so it is important to know what medications the patient is taking. * Infections and vomiting: Both can impact blood chemistry and overall health, leading to unreliable results. * Pregnancy: Pregnancy can alter various lab values, including hormone levels and other metabolic markers. Preventing Hemolysis During Collection Hemolysis occurs when red blood cells are broken open, releasing hemoglobin into the plasma. This can interfere with many lab tests, leading to inaccurate results. It is essential to follow specific guidelines to avoid hemolysis. Key Practices to Prevent Hemolysis: * Tourniquet Use: Leaving a tourniquet on the patient’s arm for more than 60 seconds can cause hemolysis. Always apply the tourniquet briefly and release it before collecting the specimen. * Alcohol Application: Allow alcohol to dry completely before performing venipuncture. Alcohol can cause hemolysis if not given enough time to evaporate. * Needle Gauge: Use an appropriate gauge needle for the patient. A needle that is too small can cause hemolysis due to the force applied during blood draw. Best Practices for Collection and Handling Dermal Puncture: * Forceful squeezing or milking during a dermal puncture can lead to hemolysis and contamination of the sample. Always perform the puncture gently and avoid squeezing the puncture site. * Vigorous Mixing: Avoid vigorous mixing of collection tubes as it can also cause hemolysis. * Syringe Transfers: When transferring blood from a syringe to a tube, do not push the plunger forcefully. This can damage blood cells and lead to hemolysis. Specimen Transport: * Gently Handle Specimens: Always handle specimens gently during transport to avoid physical damage, which could lead to inaccurate results. * Avoid Freezing or Thawing: Do not allow specimens to freeze or thaw during transport, as this can alter the composition of the specimen. * Correct Order of Draw: Ensure that you follow the correct order of draw when collecting specimens from the patient to avoid cross-contamination between tubes. Mixing and Transferring Specimens: * Always mix each tube properly after removing it from the tube holder to ensure thorough mixing of the blood with the additive. * Transfer specimens promptly from syringes to evacuated tubes to prevent clotting. * Use Tubes with Valid Expiration Dates: Always check that the tubes used have not expired. Air Purging in Winged Infusion Sets: * Purge the air out of the winged infusion set by using discard tubes, especially when filling light blue top tubes, to avoid air bubbles that could interfere with test results. Removing Tubes at the Fill Level: * Remove tubes from the holder as soon as the blood reaches the fill level to avoid overfilling, which could alter the results. Proper Technique for Minimizing Clotting in Dermal Punctures Dermal punctures are typically used for capillary blood draws (such as fingerstick or heel stick samples). Proper technique is essential to minimize clotting: * Minimize Clotting: Avoid excessive pressure or manipulation at the puncture site to reduce the chance of clotting. * Correct Tube Selection: Make sure you use the correct tube for dermal puncture collections to avoid clotting or interference with the test. Understanding and Interpreting Requisitions Accurate interpretation of test requisitions is vital for collecting the correct specimen. You must: * Correctly interpret requisitions to ensure that you are collecting the correct type of specimen for the ordered tests. * Ensure correct labeling with patient details (name, identification number, time of collection, etc.) and accurate specimen information to avoid errors. Special Considerations for Light and Temperature-Sensitive Specimens Some specimens are light-sensitive or require specific temperature conditions to remain stable: * Protect light-sensitive specimens(such as bilirubin and folate) by wrapping them in foil to avoid degradation due to exposure to light. * Store temperature-sensitive specimens (such as blood gas tests) in specific temperature conditions (e.g., room temperature for 15 to 30 minutes or in an ice slurry for up to an hour). Alcohol as an Antiseptic During specimen collection, follow the manufacturer's instructions on the use of alcohol as an antiseptic. In some cases, alcohol may not be recommended, as it could affect the sample. Always ensure that you are following the correct antiseptic procedure for the specific test being performed. Labeling Specimens Accurate labeling of specimens is one of the most crucial steps in preventing errors: * Label specimens immediately after collection with the patient's name, identification number, date and time of collection, and specimen type. * Ensure that the label is legible and that all required information is present. CLSI Order of Draw The Clinical and Laboratory Standards Institute (CLSI) provides guidelines for the correct order of draw during specimen collection. The correct order of draw minimizes the risk of contamination and cross-reactivity between different additives in the tubes. The order is as follows: 1. Blood culture bottles 2. Light blue stopper 3. Red stopper serum tubes 4. Orange rapid serum tubes 5. Green stopper 6. Lavender stopper 7. Pink stopper 8. Gray stopper Chain of Custody The chain of custody refers to the process of maintaining control and accountability for every specimen from the moment it is collected until it is disposed of or reaches its final destination (e.g., testing or analysis). The chain of custody ensures that the specimen is not tampered with during transportation or storage, which is particularly crucial for legal and forensic purposes. A well-documented chain of custody prevents errors, misidentification, and the potential for legal challenges regarding the accuracy or authenticity of test results. Chain of Custody Documentation When a specimen is collected, the chain of custody form must be filled out thoroughly. The following information must be documented to ensure proper tracking and accountability: 1. Patient Information: The name and identifying information (such as the patient ID number) of the patient or individual from whom the specimen was obtained. 2. Specimen Information: The type of specimen (e.g., blood, urine, swabs, etc.), as well as the body part or object from which the specimen was obtained. 3. Collector’s Information: The name of the person who obtained and processedthe specimen. 4. Date and Location: The date and location where the specimen was collected. 5. Attestation Information: The signature of the person who is attesting that the specimen is the correct one and that it matches its documentation. 6. Signature and Date from Every Custodian: Every person who has handled the specimen (even if just for transporting) must sign and date the form. This includes every individual who has taken possession of the specimen, no matter how brief the interaction was. Transporting and Handling Specimens in Chain of Custody When transferring specimens during the chain of custody process, it is crucial that the specimen remains properly identified and protected. Steps for Transferring Specimens: * Label the Specimen: Ensure that the specimen is labeled properly with identifying information, including the patient’s name, specimen type, and any other relevant details. * Biohazard Bag: Place the specimen in a biohazard bag with a permanent sealto prevent tampering. The seal ensures that the specimen remains intact and protected during transportation. * Specimens as Legal Evidence: Specimens handled under the chain of custody are often legal evidence and must not be tampered with. Tampering with specimens can result in legal consequences and invalidate the use of the specimen in testing. Situations Requiring Chain of Custody Certain tests require strict adherence to the chain of custody because they are used as legal evidence or in sensitive situations. These situations include: Forensic Analysis: Forensic testing may involve various specimens, such as: * Vaginal swabs (after a rape or assault) * Blood and body fluids collected from crime scenes or postmortem (after death) specimens taken during autopsies. * Toxicology testing to identify substances in cases of poisoning, overdose, or drug abuse. Forensic analysis tests are used in criminal investigations, and the specimens must be handled carefully to ensure their integrity is maintained for legal proceedings. Workplace Drug Testing: Chain of custody is vital in workplace drug testing to ensure the accuracy and integrityof results. The specimens collected for drug testing are considered legal evidence in some cases, so maintaining the chain of custody helps protect against challenges to test results. Drug Testing for Professional Athletes: In professional sports, athletes may be tested for performance-enhancing drugs (PEDs). Chain of custody procedures help ensure that the specimen collected from the athlete is handled correctly and that the results are legitimate. Neonatal Drug Testing: Testing for drug use in newborns is essential in situations where the mother may have used substances during pregnancy. Neonatal drug testing must adhere to chain of custody procedures to ensure the results are valid and reliable. Specimens for neonatal drug testing are typically collected within 24 hours of birth to detect drugs used 24 to 72 hours prior to childbirth. Urine Drug Testing Urine drug tests are commonly used to detect the presence of illegal or prescription drugs in the body. These tests may be used in various scenarios, such as workplace testing, legal cases, or medical evaluations. Privacy and Accuracy: * Privacy: It is important to ensure the privacy of the patient during urine collection, as this is a sensitive process. * Accuracy: The specimen must be handled carefully to ensure that the test results are accurate and not compromised. The chain of custody form must be signed and dated by everyone involved in the specimen collection, handling, and transport. * Detection of Drugs: Urine tests can usually detect the use of certain drugs, including: * Marijuana: Can be detected for up to a week after use. * Cocaine, heroin, and other substances: Can typically be detected for 2 days following use. Sports-Related Drug Testing Sports-related drug testing is another area where the chain of custody is critical. These tests typically detect the use of substances that can enhance athletic performance, such as stimulants. Chain of custody is essential to ensure that the sample is not tampered with or contaminated. Neonatal Drug Testing and Procedures As mentioned earlier, neonatal drug testing focuses on the presence of substances used by the mother during pregnancy. Drugs that may be detected include: * Cocaine * Opiates * Amphetamines * Methamphetamines * Phencyclidine (PCP) Collection Timing: * Neonatal drug testing should be performed within 24 hours of birth and typically looks for maternal drug use 24 to 72 hours prior to childbirth