Bio remaining vocab test 3 chpt 18,19,20

Operon

A unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway.

Repressor

A protein that inhibits gene transcription. In prokaryotes, repressors bind to the DNA in or near the promoter. In eukaryotes, repressors may bind to control elements within enhancers, to activators, or to other proteins in a way that blocks activators from binding to DNA.

Regulatory gene

A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

Inducer

A specific small molecule that binds to a bacterial repressor protein and changes the repressor's shape so that it cannot bind to an operator, thus switching an operon on.

Activator

A protein that binds to DNA and stimulates gene transcription. In prokaryotes, activators bind in or near the promoter; in eukaryotes, activators generally bind to control elements in enhancers.

Differential gene expression

The expression of different sets of genes by cells with the same genome.

Histone acetylation

The attachment of acetyl groups to certain amino acids of histone proteins.

DNA methylation

The presence of methyl groups on the DNA bases (usually cytosine) of plants, animals, and fungi. (The term also refers to the process of adding methyl groups to DNA bases.)

Epigenetic inheritance

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome.

Control elements

A segment of noncoding DNA that helps regulate transcription of a gene by serving as a binding site for a transcription factor.

Enhancers

A segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates.

Alternative RNA splicing

A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.

Proteasomes

A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.

MicroRNAs (miRNAs)

A small, single-stranded RNA molecule, generated from a hairpin structure on a precursor RNA transcribed from a particular gene.

Small interfereing RNAs (siRNAs)

One of multiple small, single-stranded RNA molecules generated by cellular machinery from a long, linear, double-stranded RNA molecule.

Differentiation

The process by which a cell or group of cells become specialized in structure and function.

Morphogenesis

The cellular and tissue-based processes by which an animal body takes shape.

Induction

The process in which one group of embryonic cells influences the development of another, usually by causing changes in gene expression.

Pattern formation

The development of a multicellular organism's spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space.

Positional information

Molecular cues that control pattern formation in an animal or plant embryonic structure by indicating a cell's location relative to the organism's body axes. These cues elicit a response by genes that regulate development.

Morphogen

A substance, such as Bicoid protein in Drosophila, that provides positional information in the form of a concentration gradient along an embryonic axis.

Oncogene

A gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer.

p53 gene

A tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of proteins that inhibit the cell cycle.

Virus

An infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat (capsid) and, for some viruses, a membranous envelope.

Capsid

The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.

Viral envelope

A membrane, derived from membranes of the host cell, that cloaks the capsid, which in turn encloses a viral genome.

Bacteriophage

A virus that infects bacteria.

Host range

The limited number of species whose cells can be infected by a particular virus.

Lytic cycle

A type of phage replicative cycle resulting in the release of new phages by lysis (and death) of the host cell.

Restriction enzyme

An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium (such as phage genomes). The enzyme cuts at specific nucleotide sequences (restriction sites).

Retrovirus

An RNA virus that replicates by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

Reverse transcriptase

An enzyme encoded by certain viruses (retroviruses) that uses RNA as a template for DNA synthesis.

HIV

The infectious agent that causes AIDS. HIV is a retrovirus.

AIDS

The symptoms and signs present during the late stages of HIV infection, defined by a specified reduction in the number of T cells and the appearance of characteristic secondary infections.

Vaccine

A harmless variant or derivative of a pathogen that stimulates a host's immune system to mount defenses against the pathogen.

Epidemic

A general outbreak of a disease.

Pandemic

A global epidemic.

Viroid

A plant pathogen consisting of a molecule of naked, circular RNA a few hundred nucleotides long.

Prion

An infectious agent that is a misfolded version of a normal cellular protein. Prions appear to increase in number by converting correctly folded versions of the protein to more prions.

Recombinant DNA

A DNA molecule made in vitro with segments from different sources.

Biotechnology

The manipulation of organisms or their components to produce useful products.

Genetic engineering

The direct manipulation of genes for practical purposes.

Plasmid

A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome; in DNA cloning, used as vectors carrying up to about 10,000 base pairs (10 kb) of DNA.

Restriction enzyme

An endonuclease (type of enzyme) that recognizes and cuts DNA molecules foreign to a bacterium (such as phage genomes).

Restriction site

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

Restriction fragments

A DNA segment that results from the cutting of DNA by a restriction enzyme.

Sticky end

A single-stranded end of a double-stranded restriction fragment.

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3′ end of one DNA fragment (such as an Okazaki fragment) to the 5′ end of another DNA fragment (such as a growing DNA chain).

Complementary DNA (cDNA)

A double-stranded DNA molecule made in vitro using mRNA as a template and the enzymes reverse transcriptase and DNA polymerase.

Nucleic acid hybridization

The process of base pairing between a gene and a complementary sequence on another nucleic acid molecule.

Nucleic acid probe

In DNA technology, a labeled single-stranded nucleic acid molecule used to locate a specific nucleotide sequence in a nucleic acid sample.

Polymerase chain reaction (PCR)

A technique for amplifying DNA in vitro by incubating it with specific primers, a heat-resistant DNA polymerase, and nucleotides.

Gel electrophoresis

A technique for separating nucleic acids or proteins on the basis of their size and electrical charge, both of which affect their rate of movement through an electric field in a gel made of agarose or another polymer.

Restriction fragment length polymorphism

A single nucleotide polymorphism (SNP) that exists in the restriction site for a particular enzyme, thus making the site unrecognizable by that enzyme and changing the lengths of the restriction fragments formed by digestion with that enzyme.

Southern blotting

A technique that enables specific nucleotide sequences to be detected in samples of DNA. It involves gel electrophoresis of DNA molecules and their transfer to a membrane (blotting), followed by nucleic acid hybridization with a labeled probe.

Northern blotting

A technique that enables specific nucleotide sequences to be detected in samples of mRNA. It involves gel electrophoresis of RNA molecules and their transfer to a membrane (blotting), followed by nucleic acid hybridization with a labeled probe.

RNA interference (RNAi)

A technique used to silence the expression of selected genes.

Genome wide association studies

A large-scale analysis of the genomes of many people having a certain phenotype or disease, with the aim of finding genetic markers that correlate with that phenotype or disease.

Single nucleotide polymorphism

A single base-pair site in a genome where nucleotide variation is found in at least 1% of the population.

Totipotent

Describing a cell that can give rise to all parts of the embryo and adult, as well as extraembryonic membranes in species that have them.

Stem cell

Any relatively unspecialized cell that can produce, during a single division, one identical daughter cell and one more specialized daughter cell that can undergo further differentiation.

Pluripotent

Describing a cell that can give rise to many, but not all, parts of an organism.

Gene therapy

The introduction of genes into an afflicted individual for therapeutic purposes.

Transgenic

Pertaining to an organism whose genome contains a gene introduced from another organism of the same or a different species.

Genetically modified (GM) organisms

An organism that has acquired one or more genes by artificial means; also known as a transgenic organism