Chapter 12 Lyso/lytic

Question 1

Once inside the host cell, the lambda phage genome circularizes by the joining of two single-stranded _______ of about 12 nucleotides in length

Answer 1

cohesive (cos) ends

Question 2

Immediate early genes are expressed shortly after circularization and produces ___ and ___ proteins

Answer 2

N and cro proteins

Question 3

What are the 2 different promoters that transcription begins at in the lambda phage genome?

Answer 3

1) Pr: rightward transcription (cro protein)
2) PL: leftward transcription (N protein)

Question 4

Regulation of lysogeny begins with the _____ protein binding to three transcription-terminating DNA sequences: tL, tR1, tR2

Answer 4

N

Question 5

The N protein is an _______

Answer 5

antiterminator

Question 6

When bound by N protein, transcription continues through terminating sequences allowing for expression of _______

Answer 6

delayed early genes

Question 7

What are the 4 delayed early genes?

Answer 7

1) integrase
2) CII
3) CIII
4) CI

Question 8

integrase and CIII protein are produced by ______ transcription
(What direction?)

Answer 8

leftward

Question 9

protein cII is produced by _______ transcription

Answer 9

rightward

Question 10

cII/cIII complex binds to promotor PRE to initiate leftward transcription of the ___ gene

Answer 10

cI gene
- cI protein is also known as λ repressor protein

Question 11

For the repressor to be active, it needs to form a _______ (active form)

Answer 11

dimer

Question 12

the _______ protein and the ________ protein undergo competetive binding at the OR1, OR2, and OR3 operators

Answer 12

lambda (cI)
cro

Question 13

IF cro protein is bound at operator OR3, it blocks access of RNA polymerase at ____ promoter, preventing the production of the λ repressor and stimulating transcription of cro from the _____ promoter

Answer 13

1) PRM
2) PR

Question 14

IF λ protein is bound at operator OR1, it blocks access of RNA polymerase at ____ promoter, preventing the production of the cro protein and stimulating transcription of λ repressor from the _____ promoter

Answer 14

1) PR
2) PRM

Question 15

One of these genes is Q, which encodes _______ protein, a positive regulator of transcription of late genes rightward of PR

late genes include production of head adn tail proteins and those required for host cell lysis

Answer 15

Q protein

Question 16

Large numbers of co-infecting phage favor entry of cell into _______

Answer 16

lysogeny

Question 17

DNA damage into the host induces _______

Answer 17

lytic cycle

Question 18

IF the health of host cell population is actively growing then _______ is induced, if poorly growing then _______ is induced

Answer 18

lytic
lysogeny

Question 19

Describe induction from lysogeny to reinitiate the lytic cycle

Answer 19

Rec A acts as a protease and cuts λ repressor

Question 20

When cro protein binds to the exposed operators, it leads to the expression of Xis, which produces the enzyme _______

Answer 20

excisionase