AP Bio Midterm Key Terms Ch. 18

Question 1

activator

Answer 1

A protein that binds to DNA and stimulates transcription of a specific gene.

Question 2

AIDS (acquired immunodeficiency syndrome)

Answer 2

The name of the late stages of HIV infection, defined by a specified reduction of T cells and the appearance of characteristic secondary infections.

Question 3

bacteriophage

Answer 3

A virus that infects bacteria; also called a phage.

Question 4

capsid

Answer 4

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

Question 5

conjugation

Answer 5

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.

Question 6

corepressor

Answer 6

A small molecule that cooperates with a repressor protein to switch on operon off.

Question 7

cyclic AMP (cAMP)

Answer 7

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.

Question 8

episome

Answer 8

A genetic element that can exist either as a plasmid or as part of the bacterial chromosome.

Question 9

F factor

Answer 9

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.

Question 10

F plasmid

Answer 10

The plasmid form of the F factor.

Question 11

HIV (human immunodeficiency virus)

Answer 11

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

Question 12

host range

Answer 12

The limited range of host cells that each type of virus can infect and parasitize.

Question 13

inducer

Answer 13

A specific small molecule that inactivates the repressor in an operon.

Question 14

insertion sequence

Answer 14

The simplest kind of transposable element, consisting of inverted repeats of DNA flanking a gene for transposase, the enzyme that catalyzes transposition.

Question 15

lysogenic cycle

Answer 15

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.

Question 16

lytic cycle

Answer 16

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

Question 17

nucleoid

Answer 17

A dense region of DNA in a prokaryotic cell.

Question 18

operator

Answer 18

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.

Question 19

operon

Answer 19

A unit of genetic function common in bacteria and phages, consisting of coordinately regulated clusters of genes with related functions.

Question 20

phage

Answer 20

A virus that infects bacteria; also called a bacteriophage.

Question 21

plasmid

Answer 21

A small ring of DNA that carries accessory genes separate from those of a bacterial chromosome; also found in some eukaryotes, such as yeast.

Question 22

prion

Answer 22

An infectious form of protein that may increase in number by converting related proteins to more prions.

Question 23

prophage

Answer 23

A phage genome that has been inserted into a specific site on the bacterial chromosome.

Question 24

provirus

Answer 24

Viral DNA that inserts into a host genome.

Question 25

R plasmid

Answer 25

A bacterial plasmid carrying genes that confer resistance to certain antibiotics.

Question 26

regulatory gene

Answer 26

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

Question 27

repressor

Answer 27

A protein that suppresses the transcription of a gene.

Question 28

retrovirus

Answer 28

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.

Question 29

reverse transcriptase

Answer 29

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

Question 30

temperate phage

Answer 30

A phage that is capable of reproducing by either the lytic or lysogenic cycle.

Question 31

transduction

Answer 31

(1) A DNA transfer process in which phages carry bacterial genes from one host cell to another. (2) In cellular communication, the conversion of a signal from outside the cell to a form that can bring about a specific cellular response.

Question 32

transformation

Answer 32

(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.

Question 33

transposable genetic element

Answer 33

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.

Question 34

transposon

Answer 34

A transposable genetic element that moves within a genome by means of a DNA intermediate.

Question 35

vaccine

Answer 35

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

Question 36

viral envelope

Answer 36

A membrane that cloaks the capsid that in turn encloses a viral genome.

Question 37

viroid

Answer 37

A plant pathogen composed of molecules of naked circular RNA only several hundred nucleotides long.

Question 38

virulent phage

Answer 38

A phage that reproduces only by a lytic cycle.