Chapter 18

Front 1

capsid

Back 1

the protein shell that encloses a viral genome, maybe rod shaped, polyhedral or more complete in shape

Front 2

viral envelope

Back 2

a membrane that cloacks the capsid that in turn encloses a virual genome

Front 3

bacteriophages

Back 3

a virus that infects bacteria; also calleda phage

Front 4

host range

Back 4

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

Front 5

lytic cycle

Back 5

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

Front 6

virulent phage

Back 6

a virus that reproduces only by a lytic cycle

Front 7

virulent phage

Back 7

a virus that reproduces only by a lytic cycle

Front 8

lysogenic cycle

Back 8

a phage replication cycle where the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host

Front 9

temperate phages

Back 9

phagse that are capable of using either the lytic or lysogenic cycle

Front 10

prophage

Back 10

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

Front 11

retroviruses

Back 11

an RNA virus that reproduces by transcriping its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer causing viruses

Front 12

reverse transcriptase

Back 12

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

Front 13

human immunodeficiency virus (HIV)

Back 13

the infectious agent that causes AIDS; an RNA retrovirus

Front 14

Acquired immunodefiiency syndrome (AIDS)

Back 14

the name of the late states of HIV infections; defined by a specified reduction of T cells and the appearance of charateristic secondary infections

Front 15

vaccines

Back 15

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

Front 16

vaccines

Back 16

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

Front 17

viroids

Back 17

plant pathogens composed of molecules of naked circular RNA only several hundred nucleotides long

Front 18

prions

Back 18

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

Front 19

nucleoid

Back 19

a dense region of DNA in a prokaryotic cell

Front 20

transformation

Back 20

a change in genotype and phenotype due to the assimilation of external DNA by a cell

Front 21

transduction

Back 21

a DNA transfer process used by phages to carry bacterial genes from one host cell to another

Front 22

generalized transduction

Back 22

the random transfer of bacterial genes from one bacterium to another

Front 23

specialized transduction

Back 23

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

Front 24

conjugation

Back 24

in bacteria the direct transfer of DNA between 2 cells that are temp joined

Front 25

F factor

Back 25

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- may exist as a plasmid or integrated into the bacterial chromosome

Front 26

plasmid

Back 26

a small ring of DNA that carries accessory genes separate from those of a bacterial chromosome; also foud in some eukaroytes such as yeast

Front 27

episome

Back 27

a genetic element that can exist either as a plasmid or as part o fthe bacterial chromosome

Front 28

F plasmid

Back 28

the plasmid form of the F factor

Front 29

R plasmid

Back 29

a bacterial plasmid carrying genes that confer resistence to certain antibotics

Front 30

R plasmid

Back 30

a bacterial plasmid carrying gnees that confer resistence to certain antibotics

Front 31

transposon

Back 31

a transopable genetic element; a mobile segment of DNA that serves as an agent of genetic change

Front 32

insertion sequence

Back 32

a mutation involving the addition of 1 or more nucleotide pairs to a gene

Front 33

operator

Back 33

in prokaroytic DNA a sequence of nucleotides near the start of an operon to which an active repressor can attach

Front 34

operon

Back 34

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

Front 35

repressor

Back 35

a protein that suppresses the transcription of a gene

Front 36

regulatory gene

Back 36

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

Front 37

corepressor

Back 37

a small molecule that cooperates with a repressor protein to switch an operon on

Front 38

inducer

Back 38

a specific small molecule that inactivates the repressor in an operon

Front 39

cycli AMP (cAMP)

Back 39

cyclic adenosine monophosphate, a ring shaped molecule made from ATP that is a common intracullular signaling molecule (second messenger) in eukaryotic cells (for example in vertebrate endocrine cells) alos regulator of some bacterial operons