Ch 18

Front 1

capsid

Back 1

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

Front 2

viral envelope

Back 2

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

Front 3

bacteriophage

Back 3

A virus that infects bacteria; also called a phage. See phage.

Front 4

AIDS (acquired immunodeficiency syndrome)

Back 4

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

Front 5

cAMP receptor protein (CRP)

Back 5

A regulatory protein that directly stimulates gene expression.

Front 6

compressor

Back 6

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

Front 7

conjugation

Back 7

In bacteria, the direct transfer of DNA between two cells that are temporarily joined.

Front 8

cyclic AMP (cAMP)

Back 8

yclic 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.

Front 9

episome

Back 9

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

Front 10

F factor

Back 10

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 integrated into the bacterial chromosome.

Front 11

F1 plasmid

Back 11

The plasmid form of an F factor.

Front 12

generalized transduction

Back 12

The random transfer of bacterial genes from one bacterium to another.

Front 13

HIV (human immunodeficiency virus)

Back 13

The infectious agent that causes AIDS; HIV is an RNA retrovirus.

Front 14

host range

Back 14

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

Front 15

inducer

Back 15

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

Front 16

insertion sequence

Back 16

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

Front 17

lysogenic cycle

Back 17

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.

Front 18

lytic cycle

Back 18

A type of viral replication cycle resulting in the release of new phages by death or lysis of the host cell.

Front 19

nucleoid

Back 19

A dense region of DNA in a prokaryotic cell.

Front 20

operator

Back 20

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.

Front 21

operon

Back 21

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

Front 22

phage

Back 22

A virus that infects bacteria; also called a bacteriophage.

Front 23

plasmid

Back 23

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

Front 24

prion

Back 24

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

Front 25

prophage

Back 25

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

Front 26

provirus

Back 26

Viral DNA that inserts into a host genome.

Front 27

R plasmid

Back 27

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

Front 28

regulatory gene

Back 28

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

Front 29

repressor

Back 29

A protein that suppresses the transcription of a gene.

Front 30

retrovirus

Back 30

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.

Front 31

reverse transcriptase

Back 31

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

Front 32

specialized transduction

Back 32

The transfer of only those genes near the prophage site on the bacterial chromosome.

Front 33

temperate phages

Back 33

Phages that are capable of using either the lytic or lysogenic cycle.

Front 34

transduction

Back 34

A DNA-transfer process used by phages to carry bacterial genes from one host cell to another.

Front 35

transformation

Back 35

(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.

Front 36

transposon

Back 36

A transposable genetic element; a mobile segment of DNA that serves as an agent of genetic change.

Front 37

vaccine

Back 37

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

Front 38

viral envelope

Back 38

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

Front 39

virulent virus

Back 39

A virus that reproduces only by a lytic cycle.