Bio Chap 7-11

DNA (deoxyribonucleic acid)

found in nucleus of eukaryotic cells, in the form of a chromosome (single DNA molecules wrapped around proteins)

hereditary molecules that are passed from parents to offspring, common to all living organisms, serves as the instruction manual for how to build an individual

Human Sex Chromosomes

23rd pair of chromosomes determines sex, XX= female, XY= male

Human chromosomes

humans have 23 pairs of chromosomes. One chromosome from each pair is inherited from the biological mother, and the other from the father

Genome

complete set of genetic instructions encoded in all the chromosomes of an organism

nucleotides

each _____ consists of a sugar, a phosphate, and a base

DNA shape

two strands of nucleotides pair up and twist around each other to form a spiral-shaped double helix. Sugars and phosphates form the outside ‘backbone’. Baes form the internal ‘rungs’.

DNA nitrogenous bases

adenine, thymine, guanine, cytosine. A pairs with T and C pairs with G.

two strands of DNA double helix are held together by base pairing (hydrogen bonding) between bases of each strand. the order of bases is unique to each individual and determines their characteristics

DNA profile

visual representation of a person’s unique DNA sequence. To make DNA profile, we need many copies of their DNA. To learn how to make copies of DNA, we need to know how DNA is replicated in cells.

Semiconservative mechanism

DNA replication produces two copies of the original DNA molecule. Each molecule consists of one of the strands of the original DNA molecule and a new strand.

DNA Replication

natural process by which cells make an identical copy of a DNA molecule. Takes advantage of complementary base-pairing rules.

1. hydrogen bonds that gold base pairs are broken, and helicase enzyme unwinds the DNA helix

2. DNA polymerase enzyme reads the DNA and adds complementary nucleotides using the rules of base pairing (A to T, C to G)

Polymerase Chain Reaction (PCR)

a laboratory technique scientists use to amplify (replicate) a specific DNA segment to study it.

• Ingredients: DNA, free nucleotides to add to new DNA strands, Polymerase enzyme, primers (short segments of DNA that guide DNA polymerase to the section of DNA to copy)

• Lab Procedures: temperature cycles cause the DNA strand to replicate. Heating for a time separates DNA strands. Cooling for a time allows DNA polymerase to pair new nucleotides with the original template strands.

• Results: allows DNA replication to occur many times. Can make billions of copies from a starting sample of just a few molecules of DNA.

Short tandem repeats (STR)

a good type of DNA segment to use for DNA profiling. (can use PCR to target STR)

Making a DNA Profile

Collect Sample:

• collect cells and extract DNA (ex. saliva at a crime scene); care must be taken not to contaminate samples with DNA from other people

Amplify Sample

• Amplify STR regions by PCR. The more regions we amplify, the more certain we can be about the result.

Separate DNA Fragments

• Separate STRs using gel electrophoresis (lab technique that separates DNA fragments by size). Smaller fragments travel farther in the gel than larger fragments

• Compare STR banding patterns. Bands of DNA are visible using fluorescence. Different lengths for each STR region and each person create a specific pattern of bands.

DNA evidence

more reliable than other forms of evidence. Error rates for bite mark identification can be as high as 91%, hair analysis can only exclude a suspect not positively identify one. Except for identical twins, no two people share exactly the same DNA.

Protein

a macromolecule made of repeating amino acid subunits. They have many functions, such as muscle contraction, facilitate chemical reactions, and fight infections.

Amino Acid

building blocks of proteins. they are 20 different amino acids all with the same basic core structure but a unique chemical side group.

Amino Acid Sequence

amino acids bond together to form a linear chain. Chain folds into 3-D protein based on the sequence of amino acids. Determine the shape and function of a protein.

Protein folding

changing an amino acid in the sequence changes the 3-D shape of the protein which determines its function

Genes

encode instructions for proteins. A sequence of DNA that contains the instructions to make one or more proteins. Found on chromosomes. Each chromosome carries a unique set of genes.

Gene expression

synthesis of a protein from a gene. The process of converting information from the coding sequence of a gene into a protein. Happens in 2 steps:

1. Transcription involves converting DNA to RNA.It occurs in the nucleus of eukaryotic cells and the cytoplasm of prokaryotic cells.

2. Translation involves converting RNA to protein. Occurs on ribosomes in cytoplasm.

Gene structure

1. Regulatory sequence on-off switch for the gene

2. Coding sequence controls the amino acid sequence of the protein

Gene expression: Transcription

Molecules of messenger RNA (mRNA) are synthesized from the instructions encoded in genes. RNA polymerase binds to the regulatory sequence of the genes coding region. The DNA strands unwind, exposing the coding sequence of the gene. RNA polymerase copies a strand of DNA into a complementary strand of mRNA by ‘reading’ the gene coding sequence. Complementary mRNA forms from a DNA template according to the rules of base paring (A-U, not A-T). The mRNA strand is formed and detaches from the DNA sequence. DNA reforms its double helix. The completed mRNA leaves the nucleus. The DNA sequence of the gene is unchanged, and it remains in its chromosome in the nucleus.

Gene expression: Translation

The mRNA molecule associates with a ribosome. The ribosome moves along the mRNA ‘reading’ it in groups of 3 nucleotides (codons). Each codon specifies a particular amino acid. Transfer RNA (tRNA)carries an amino acid to the mRNA and ribosome by using its anticodon to find a matching mRNA codon. When the correct tRNA is in place, the specified amino acid is added to the growing chain. The ribosome moves on to the next codon. The completed amino acid chain detaches from the ribosome and folds into its 3-D shape.

Universal Genetic Code

set of rules relating particular mRNA codons to particular amino acids. 64 possible codons code for 20 different amino acids.

Genetic engineering

manipulating the genome of a living organism; Ex: Moon Parka winter coat made of genetically modified spider silk

Transgenic or genetically modified organisms (GMOs)

organisms that have received recombinant genes; Ex: corn, tomatoes, wheat, potatoes

Spider silk factories

1. create a recombinant gene. combine the yeast regulatory sequence with the spidroin coding sequence.

2. Insert the recombinant gene into living cells. Insert the recombinant gene into a loop of DNA (vector). Insert the vector into a yeast cell

3. Produce protein product. Transgenic yeast cultivated under special conditions produce the spidrion protein in large quantities.

Recombinant gene

a gene that contains parts of different genes that aren’t found together in nature

Cancer

disease of unregulated cell division. Genetic mutations are often a main reason for cancer. Other risk factors play a large role, too.

BRCA Mutations

Genes BRCA1 and BRCA2 have been identified as being indicators of breast cancer risk. It is located on chromosomes 17 and 13. Having a BRCA mutation increases the chance that on individual will develop breast cancer and other cancers.

Cell Division

cells divide to reproduce themselves for various reasons: growth and development, cell replacement, heal wounds. Cell division includes:

1. Interphase: growth and preparation

2. Mitosis: separate copies of chromosomes

3. cytokinesis: divide into two cells

Cell Division: Interphase

preparatory steps before cell division. Contains G_¹, S, and G₂ phases. Involves growth and duplications of chromosomes.

• G₁ Phase: cell grows, makes extra cytoplasm

• S phase: DNA replication occurs, chromosomes form identical sister chromatids

• G₂ phase: cell prepares for division

Cell Division: Mitosis

chromosomes line up. Small fibers attach to centromeres on each sister chromatid. One of each sister chromatid ends up in each side of the cell.

Cell Division: Cytokinesis

enlarged cell splits into two cells. Each has full complement of DNA. Starts with one parent cell undergoing mitosis. Ends with 2 daughter cells.

Chromosomes perspective

DNA replicates during S phase in interphase. Sister chromatids (exact copies of chromosomes) separate during mitosis. Cells divide into two during cytokinesis.

Mitosis

• Interphase: chromosomes are loosely gathered in the nucleus

• Prophase: Chromosomes begin to coil up

• Metaphase: chromosomes align in the middle of the cell

• Anaphase: Fibers called microtubules shorten, separating sister chromatids.

• Telophase: daughter cell nuclei are formed

• Cytokinesis: cytoplasm divides, and daughter cells are formed. This occurs during the telophase

Proto-oncogenes

(go signals); normally promote cell division and differentiation. Can be mutated to become permanently activated. When mutated, they become oncogenes (genes that cause cancer)

Tumor suppressor genes

(stop signals); normally pause cell division, repair DNA, or initiate cell death. Can be mutated to become inactivated. Ex. BRCA1 and BRCA2

Cancer development

It takes more than a single mutation to cause cancer. Individuals who have inherited high risk mutations require fewer additional mutations to get cancer, and therefore develop cancer at an earlier age. `

Benign tumor

noncancerous tumor

Malignant tumor

cancerous tumor with cells that can spread over the body

Metastasis

the spread of cancer cells from one location of the body to another

Treating Cancer: Surgery

can remove cancerous tissue. Most effective for solid tumors that are detected early. Ineffective for widespread cancers.

Treating Cancer: Chemotherapy

uses toxic chemicals to kill rapidly dividing cells. Can affect cancer cells that are spread throughout the body. Side effects are severe.

Treating Cancer: Radiation Therapy

Uses high-energy ionizing radiation to kill targeted cells. Kills cells by damaging the DNA in cells. Side effects are severe.

Treating Cancer: Targeted therapy

Kill cancer cells by exploiting weakness caused by oncogenes or mutated tumor suppressor genes. Normal cells are unaffected because their gene expression is normal.

Immunotherapy

cancer cells prevent the immune system from killing them. _____ re-enables the ability of immune cells to kill cancer cells

Cystic Fibrosis

A genetic disease caused by a single gene mutation (change in nucleotide sequence of DNA, creates a new mutant allele), allele of the CFTR gene. CFTR gene codes the transmembrane regulator protein, which moves ions in and out of cells. People with CF have a mutated version of CFTR that fails to move ions. Caused by a recessive allele.

Diploid organisms

have two copies of every chromosome

Homologous chromosomes

are a pair of chromosomes that contain the same genes; one chromosome inherited from mom and one chromosome inherited from dad

Alleles

are alternative versions of the same gene that have different nucleotide sequences; humans are diploid meaning that we have 2 alleles for each gene

Humans are Diploid Organisms

In a diploid cell, one homologous chromosome is inherited from the mother, and the other one from the father. In the case of CF, having one normal allele is sufficient to remain healthy.

Genotype

is the particular genetic or allele makeup of an individual. Ex: which CFTR alleles you have

Phenotype

the observable or measurable features of an individual. Ex whether or not you have CF

Inheriting Genes

Genes are located on chromosomes, which are physically transmitted from parent to offspring. Diploid organisms have two copies of each chromosome. One chromosome from each parent (homologous chromosomes) is passed to offspring.

Sexual Reproduction

combination of maternal and parental alleles that join during fertilization. Alleles from parents determine genotype and contribute strongly to phenotype. Requires egg and sperm, which are gametes. Gametes formed by meiosis. Haploid sperm fertilizes haploid egg resulting in a diploid zygote. Zygote divides by mitosis into an embryo.

Gametes

reproductive cells that carry only one copy of each chromosome (haploid)

Meiosis

special cell division producing genetically unique haploid cells. Two separate divisions: Meiosis 1 and 2

Meiosis 1

Unlike mitosis, meiosis 1 separates homologous chromosomes instead of sister chromatids. Each daughter cell is haploid. Each chromosome still has 2 sister chromosomes still has two sister chromatids. has a PMAT 1; 46 chromosomes

Meiosis 2

Separates sister chromatids. 4 haploid daughter cells. Develop into egg and sperm; PMAT 2; 23 chromosomes

Meiosis and Genetic diversity

No two gametes are identical. Due to recombination and independent assortment. These parts of meiosis are the reason that not every offspring has CF, even if the parents are carriers.

Recombination

when maternal and paternal chromosomes pair and physically exchange DNA segments

Independent assortment

alleles of different genes are distributed independently of one another

Recessive allele

affects phenotype only if the organism has two copies of that allele. Hidden by normal or dominant allele. designated by lowercase letter

Dominant allele

hides recessive allele. designated by uppercase letter.

Heterozygote

two different alleles (Aa); phenotype is normal; individual is a carrier

Homozygote

two identical alleles

• Homozygous dominant (AA): phenotype is normal

• Homozygous recessive (aa): phenotype is CF (mutant)

Punnett square

a diagram to determine the probabilities of offspring having particular genotypes. Based on genotypes of the parents. Matches up all possible gametes

Recessive Genetic Disorders

• Albinism: Lack of pigment in skin, hair, and eyes

• Cystic fibrosis: excessive mucus in lungs, digestive tract, and liver; increased susceptibility to infections

• Sickle cell disease: sickled red blood cells, damaged to tissue

• Tay-Sachs disease: Lipid accumulation in brain cells; mental deficiency, blindness, and death in childhood

Dominant Genetic Disorders

• Huntington disease: mental deterioration and uncontrollable movements; onset at middle age

• Freckles: pigmented spots on skin, particularly on face and arms

• Polydactyly: more than 5 digits on hands or feet

• Dimples: indentation in the skin of the cheeks

• Chin cleft: indentation in chin