Chapter 18 and 19

Question 1

capsid

Answer 1

protein shell that encloses the viral genome

Question 2

elongated capsid head

Answer 2

encloses DNA on phages

Question 3

protein tailpiece on phages

Answer 3

attaches the phage to the host and injects DNA inside

Question 4

viral envelopes

Answer 4

surround capsids and help infect hosts

Question 5

why aren’t viruses considered living?

Answer 5

cannot replicate by themselves

need a host to replicate DNA

Question 6

lytic cycle

Answer 6

phage reproductive cycle that results in the death of the host cell

Question 7

stages of the lytic cycle

Answer 7

1. attachment
2. phage DNA enters host DNA
3. synthesis of viral genomes and proteins
4. assembly of new virus
5. release, killing host cell

Question 8

lysogenic cycle

Answer 8

replicates phage without destroying host

genetic recombination

Question 9

prophage

Answer 9

viral DNA molecule integrated into the host cell’s DNA

Question 10

two variables to classify viruses

Answer 10

RNA or DNA

single or double stranded

Question 11

control elements of a eukaryotic gene

Answer 11

segments of noncoding DNA that regulate transcription by binding certain proteins

Question 12

roles of transcription factors

Answer 12

transcription of all protein coding genes

depend on control elements

Question 13

proximal control elements

Answer 13

located by the promoter

Question 14

distal control elements (enhancers)

Answer 14

may be far away from a gene or in an intron

Question 15

activator

Answer 15

protein that binds to an enhancer and stimulates transcription of a gene

Question 16

repressor

Answer 16

inhibits expression of certain genes

block activators

bind directly to their own enhancers

Question 17

operons

Answer 17

on/off switch
promoter
genes for metabolic enzymes

Question 18

corepressor

Answer 18

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