AP Biology Unit 9 Key Terms Flashcards
activator
A protein that binds to DNA and stimulates transcription of a specific gene.
AIDS (acquired immunodeficiency syndrome)
The name of the late stages of HIV infection, defined by a specified reduction of T cells and the appearance of characteristic secondary infections.
bacteriophage
A virus that infects bacteria; also called a phage.
capsid
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.
conjugation
In prokaryotes, the direct transfer of DNA between two cells that are temporarily joined. In ciliates, a sexual process in which two cells exchange haploid micronuclei.
corepressor
A small molecule that cooperates with a repressor protein to switch on operon off.
cyclic AMP (cAMP)
Cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells (for example, in vertebrate endocrine cells). It is also a regulator of some bacterial operons.
episome
A genetic element that can exist either as a plasmid or as part of the bacterial chromosome.
F factor
A fertility factor in bacteria; a DNA segment that confers the ability to form pili for conjugation and associated functions required for the transfer of DNA from donor to recipient. It may exist as a plasmid or be integrated into the bacterial chromosome.
F plasmid
The plasmid form of the F factor.
HIV (human immunodeficiency virus)
The infectious agent that causes AIDS. HIV is a retrovirus.
host range
The limited range of host cells that each type of virus can infect and parasitize.
inducer
A specific small molecule that inactivates the repressor in an operon.
insertion sequence
The simplest kind of transposable element, consisting of inverted repeats of DNA flanking a gene for transposase, the enzyme that catalyzes transposition.
lysogenic cycle
A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.
lytic cycle
A type of viral (phage) replication cycle resulting in the release of new phages by lysis (and death) of the host cell.
nucleoid
A dense region of DNA in a prokaryotic cell.
operator
In prokaryotic DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon.
operon
A unit of genetic function common in bacteria and phages, consisting of coordinately regulated clusters of genes with related functions.
phage
A virus that infects bacteria; also called a bacteriophage.
plasmid
A small ring of DNA that carries accessory genes separate from those of a bacterial chromosome; also found in some eukaryotes, such as yeast.
prion
An infectious form of protein that may increase in number by converting related proteins to more prions.
prophage
A phage genome that has been inserted into a specific site on the bacterial chromosome.
provirus
Viral DNA that inserts into a host genome.
R plasmid
A bacterial plasmid carrying genes that confer resistance to certain antibiotics.
regulatory gene
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.
repressor
A protein that suppresses the transcription of a gene.
retrovirus
An RNA virus that reproduces 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 some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis.
temperate phage
A phage that is capable of reproducing by either the lytic or lysogenic cycle.
transduction
A DNA transfer process in which phages carry bacterial genes from one host cell to another.
transformation
(1) The conversion of a normal animal cell to a cancerous cell. (2) A change in genotype and phenotype due to the assimilation of external DNA by a cell.
transposable genetic element
A segment of DNA that can move within the genome of a cell by means of a DNA or RNA intermediate; also called a transposable element.
transposon
A transposable genetic element that moves within a genome by means of a DNA intermediate.
vaccine
A harmless variant or derivative of a pathogen that stimulates a host’s immune system to mount defenses against the pathogen.
viral envelope
A membrane that cloaks the capsid that in turn encloses a viral genome.
viroid
A plant pathogen composed of molecules of naked circular RNA only several hundred nucleotides long.
virulent phage
A phage that reproduces only by a lytic cycle.
activator
A protein that binds to DNA and stimulates transcription of a specific gene.
alternative RNA splicing
A type of 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.
cell differentiation
The structural and functional divergence of cells as they become specialized during a multicellular organism’s development; dependent on the control of gene expression.
chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing, chromatin exists as a mass of very long, thin fibers that are not visible with a light microscope.
control element
A segment of noncoding DNA that helps regulate transcription of a gene by binding proteins called transcription factors.
differential gene expression
The expression of different sets of genes by cells with the same genome.
enhancer
A DNA segment containing multiple control elements that may be located far away from the gene it regulates.
epigenetic inheritance
Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.
euchromatin
The more open, unraveled form of eukaryotic chromatin that is available for transcription.
genomic imprinting
Phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.
heterochromatin
Nontranscribed eukaryotic chromatin that is so highly compacted that it is visible with a light microscope during interphase.
histone
A small protein with a high proportion of positively charged amino acids that binds to the negatively charged DNA and plays a key role in its chromatin structure.
histone acetylation
The attachment of acetyl groups to certain amino acids of histone proteins.
micro-RNA (miRNA)
A small, single-stranded RNA molecule that binds to a complementary sequence in mRNA molecules and directs associated proteins to degrade or prevent translation of the target mRNA.
multigene family
A collection of genes with similar or identical sequences, presumably of common origin.
nucleosome
A collection of genes with similar or identical sequences, presumably of common origin.
oncogene
A gene found in viruses or as part of the normal genome that is involved in triggering cancerous characteristics.
p53 gene
The guardian angel of the genome, a gene that is expressed when a cell’s DNA is damaged. Its product, p53 protein, functions as a transcription factor for several genes.
proteasome
A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.
proto-oncogene
A normal cellular gene corresponding to an oncogene; a gene with a potential to cause cancer but that requires some alteration to become an oncogene.
pseudogene
A DNA segment very similar to a real gene but which does not yield a functional product; a gene that has become inactivated in a particular species because of mutation.
Ras gene
A gene that codes for Ras protein, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases that ultimately results in the stimulation of the cell cycle. Many ras oncogenes have a point mutation that leads to a hyperactive version of the Ras protein that can lead to excessive cell division.
repetitive DNA
Nucleotide sequences, usually noncoding, that are present in many copies in a eukaryotic genome. The repeated units may be short and arranged tandemly (in series) or long and dispersed in the genome.
repressor
A protein that suppresses the transcription of a gene.
retrotransposon
A transposable element that moves within a genome by means of an RNA intermediate, a transcript of the retrotransposon DNA.
RNA interference (RNAi)
A technique to silence the expression of selected genes in nonmammalian organisms. The method uses synthetic double-stranded RNA molecules matching the sequence of a particular gene to trigger the breakdown of the gene’s messenger RNA.
transcription factor
A regulatory protein that binds to DNA and stimulates transcription of specific genes.
transposon
A transposable genetic element that moves within a genome by means of a DNA intermediate.
tumor-suppressor gene
A gene whose protein products inhibit cell division, thereby preventing uncontrolled cell growth (cancer).
bacterial artificial chromosome (BAC)
An artificial version of a bacterial chromosome that can carry inserts of 100, 000 to 500, 000 base pairs.
biotechnology
The manipulation of living organisms or their components to produce useful products.
cDNA library
A limited gene library using complementary DNA. The library includes only the genes that were transcribed in the cells examined.
clone
(1) A lineage of genetically identical individuals or cells. (2) In popular usage, a single individual organism that is genetically identical to another individual. (3) As a verb, to make one or more genetic replicas of an individual or cell. See also gene cloning.
cloning vector
An agent used to transfer DNA in genetic engineering. A plasmid that moves recombinant DNA from a test tube back into a cell is an example of a cloning vector, as is a virus that transfers recombinant DNA by infection.
complementary DNA (cDNA)
A DNA molecule made in vitro using mRNA as a template and the enzyme reverse transcriptase. A cDNA molecule therefore corresponds to a gene, but lacks the introns present in the DNA of the genome.
denaturation
In proteins, a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. In DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme conditions of pH, salt concentration, and temperature.
DNA fingerprint
An individual’s unique collection of DNA restriction fragments, detected by electrophoresis and nucleic acid probes.
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3’ end of a new DNA fragment to the 5’ end of a growing chain.
DNA microarray assay
A method to detect and measure the expression of thousands of genes at one time. Tiny amounts of a large number of single-stranded DNA fragments representing different genes are fixed to a glass slide. These fragments, ideally representing all the genes of an organism, are tested for hybridization with various samples of cDNA molecules.
electroporation
A technique to introduce recombinant DNA into cells by applying a brief electrical pulse to a solution containing cells. The electricity creates temporary holes in the cells’ plasma membranes, through which DNA can enter.
expression vector
A cloning vector that contains the requisite prokaryotic promoter just upstream of a restriction site where a eukaryotic gene can be inserted.
gel electrophoresis
The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.
gene cloning
The production of multiple copies of a gene.
gene therapy
The alteration of the genes of a person afflicted with a genetic disease.
genetic engineering
The direct manipulation of genes for practical purposes.
genetically modified (GM) organism
An organism that has acquired one or more genes by artificial means; also known as a transgenic organism.
genomic library
A set of thousands of DNA segments from a genome, each carried by a plasmid, phage, or other cloning vector.
genomics
The study of whole sets of genes and their interactions.
Human Genome Project
An international collaborative effort to map and sequence the DNA of the entire human genome.
in vitro mutagenesis
A technique to discover the function of a gene by introducing specific changes into the sequence of a cloned gene, reinserting the mutated gene into a cell, and studying the phenotype of the mutant.
linkage map
A genetic map based on the frequencies of recombination between markers during crossing over of homologous chromosomes.
nucleic acid hybridization
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 tag a specific nucleotide sequence in a nucleic acid sample. Molecules of the probe hydrogen-bond to the complementary sequence wherever it occurs; radioactive or other labeling of the probe allows its location to be detected.
physical map
A genetic map in which the actual physical distances between genes or other genetic markers are expressed, usually as the number of base pairs along the DNA.
polymerase chain reaction (PCR)
A technique for amplifying DNA in vitro by incubating with special primers, DNA polymerase molecules, and nucleotides.
proteomics
The systematic study of the full protein sets (proteomes) encoded by genomes.
recombinant DNA
A DNA molecule made in vitro with segments from different sources.
restriction enzyme
A degradative enzyme that recognizes and cuts up DNA (including that of certain phages) that is foreign to a bacterium.
restriction fragment
DNA segment resulting from cutting of DNA by a restriction enzyme.
restriction fragment length polymorphisms (RFLPs)
Differences in DNA sequence on homologous chromosomes that can result in different patterns of restriction fragment lengths (DNA segments resulting from treatment with restriction enzymes); useful as genetic markers for making linkage maps.
restriction site
A specific sequence on a DNA strand that is recognized as a cut siteby a restriction enzyme.
RNA interference (RNAi)
A technique to silence the expression of selected genes in nonmammalian organisms. The method uses synthetic double-stranded RNA molecules matching the sequence of a particular gene to trigger the breakdown of the gene’s messenger RNA.
single nucleotide polymorphisms (SNPs)
One base-pair variation in the genome sequence.
Southern blotting
A hybridization technique that enables researchers to determine the presence of certain nucleotide sequences in a sample of DNA.
sticky end
A single-stranded end of a double-stranded DNA restriction fragment.
Ti plasmid
A plasmid of a tumor-inducing bacterium that integrates a segment of its DNA into the host chromosome of a plant; frequently used as a carrier for genetic engineering in plants.
yeast artificial chromosome (YAC)
A vector that combines the essentials of a eukaryotic chromosome–an origin for DNA replication, a centromere, and two telomeres–with foreign DNA.
