Biology Chp 10 & 12

Nucelotides

An organic monomer consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. Nucleotides are the building blocks of nucleic acids, including DNA and RNA.

Polynucelotide

A polymer made up of many nucleotides covalently bonded together.

Sugar-Phosphate Backbone

The alternating chain of sugar and phosphate to which DNA and RNA nitrogenous bases are attached.

Thymine

A single-ring nitrogenous base found in DNA.

Cytosine

A single-ring nitrogenous base found in DNA and RNA.

Adenine

A double-ring nitrogenous base found in DNA and RNA.

Guanine

A double-ring nitrogenous base found in DNA and RNA.

Uracil

A single-ring nitrogenous base found in RNA.

Double Helix

The form assumed by DNA in living cells, referring to its two adjacent polynucleotide strands wound into a spiral shape.

DNA Polymerases

An enzyme that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.

Transcription

The synthesis of RNA on a DNA template.

Translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids. See also genetic code.

Codons

A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

Genetic Code

The set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acids in protein.

RNA Polymerase

An enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template.

Promoter

A specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA polymerase and the place where transcription begins.

Terminator

A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene.

messenger RNA (mRNA)

The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences.

Introns

In eukaryotes, a nonexpressed (noncoding) portion of a gene that is excised from the RNA transcript.

Exons

In eukaryotes, a coding portion of a gene.

RNA Splicing

The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence; occurs before mRNA leaves the nucleus.

transfer RNA (tRNA)

A type of ribonucleic acid that functions as an interpreter in translation. Each tRNA molecule has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.

Anticodon

On a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA.

ribosomal RNA (rRNA)

The type of ribonucleic acid that, together with proteins, makes up ribosomes.

Start Codon

On mRNA, the specific three-nucleotide sequence (AUG) to which an initiator tRNA molecule binds, starting translation of genetic information.

Stop Codon

In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.

Mutation

Any change to the genetic information of a cell or virus.

Mutagens

A chemical or physical agent that interacts with DNA and causes a mutation.

Virus

A microscopic particle capable of infecting cells of living organisms and inserting its genetic material. Viruses have a very simple structure and are generally not considered to be alive because they do not display all of the characteristics associated with life.

Bacteriaphages

A virus that infects bacteria; also called a phage.

Lytic Cylce

A viral reproductive cycle resulting in the release of new viruses by lysis (breaking open) of the host cell.

Lysogenic Cylce

A bacteriophage reproductive cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome.

AIDS

Acquired immunodeficiency syndrome; the late stages of HIV infection, characterized by a reduced number of T cells; usually results in death caused by infections that would be defeated by a properly functioning immune system.

HIV

Human immunodeficiency virus; the retrovirus that attacks the human immune system and causes AIDS.

Retrovirus

An RNA virus that reproduces by means of a DNA molecule. It reverse-transcribes its RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA. HIV and a number of cancer-causing viruses are retroviruses.

Reverse Transcriptase

An enzyme that catalyzes the synthesis of DNA on an RNA template.

Prions

An infectious form of protein that may multiply by converting related proteins to more prions. Prions cause several related diseases in different animals, including scrapie in sheep, mad cow disease, and Creutzfeldt-Jakob disease in humans.

Biotechnology

The manipulation of living organisms to perform useful tasks.

Genetically Modified Organisms (GMO)

An organism that has acquired one or more genes by artificial means. If the gene is from another organism, typically of another species, the recombinant organism is also known as a transgenic organism. See also transgenic organism.

Transgenic Organism

An organism that contains genes from another organism, typically of another species.

Recombinant DNA

A DNA molecule carrying genes derived from two or more sources, often from different species.

Genetic Engineering

The direct manipulation of genes for practical purposes.

Plasmids

A small ring of self-replicating DNA separate from the larger chromosome(s). Plasmids are most frequently derived from bacteria.

DNA Cloning

The production of many identical copies of a specific segment of DNA.

Vectors

A piece of DNA, usually a plasmid or a viral genome, that is used to move genes from one cell to another.

Clone

As a verb, to produce genetically identical copies of a cell, organism, or DNA molecule. As a noun, the collection of cells, organisms, or molecules resulting from cloning; also (colloquially), a single organism that is genetically identical to another because it arose from the cloning of a somatic cell.

Gene Cloning

The production of multiple copies of a gene.

Restriction Enzyme

A bacterial enzyme that cuts up foreign DNA at one very specific nucleotide sequence. Restriction enzymes are used in DNA technology to cut DNA molecules in reproducible ways.

Restriction Site

A specific sequence on a DNA strand that is recognized and cut by a restriction enzyme.

Restriction Fragments

A molecule of DNA produced from a longer DNA molecule cut up by a restriction enzyme.

DNA Ligase

An enzyme, essential for DNA replication, that creates new chemical bonds between adjacent DNA nucleotides; used in genetic engineering to paste a specific piece of DNA containing a gene of interest into a bacterial plasmid or other vector.

CRISPR-Cas9 system

A technique for editing genes in living cells, involving a bacterial protein called Cas9 associated with a guide RNA complementary to a gene sequence of interest.

Human Gene Therapy

A recombinant DNA procedure intended to treat disease by altering an afflicted person’s genes.

DNA Profiling

A procedure that analyzes an individual’s unique collection of genetic markers using PCR and gel electrophoresis. DNA profiling can be used to determine whether two samples of genetic material came from the same individual.

Forensics

The scientific analysis of evidence for crime scene investigations and other legal proceedings.

Polymerase Chain Reaction (PCR)

A technique used to obtain many copies of a DNA molecule or many copies of part of a DNA molecule. A small amount of DNA mixed with the enzyme DNA polymerase, DNA nucleotides, and a few other ingredients replicates repeatedly in a test tube.

Primers

A short stretch of nucleic acid bound by complementary base pairing to a DNA sequence and elongated with DNA nucleotides. During PCR, primers flank the desired sequence to be copied.

Repetitive DNA

Nucleotide sequences that are present in many copies in the DNA of a genome. The repeated sequences may be long or short and may be located next to each other or dispersed in the DNA.

Short Tandem Repeat (STR)

DNA consisting of tandem (in a row) repeats of a short sequence of nucleotides.

STR Analysis

A method of DNA profiling that compares the lengths of STR sequences at specific sites in the genome.

Gel Electropheresis

A technique for sorting macromolecules. A mixture of molecules is placed on a gel between a positively charged electrode and a negatively charged one; negatively charged molecules migrate toward the positive electrode. The molecules separate in the gel according to their rates of migration.

Bioinformatics

A scientific field of study that uses mathematics to develop methods for organizing and analyzing large sets of biological data.

DNA Sequencing

Determining the complete nucleotide sequence of a gene or DNA segment.

Genomics

The study of whole sets of genes and their interactions.

Whole-Genome Shotgun Method

A method for determining the DNA sequence of an entire genome by cutting it into small fragments, sequencing each fragment, and then placing the fragments in the proper order.

Human Genome Project

An international collaborative effort that sequenced the DNA of the entire human genome.

Proteomics

The systematic study of the full protein sets (proteomes) encoded by genomes.

Systems Biology

An approach to studying biology that aims to model the dynamic behavior of whole biological systems based on a study of the interactions among the system’s parts.