Deck 8: Bacteriophage Lambda

Question 1

Which of the following terms describes a bacterial cell that has a repressed copy of a bacteriophage genome integrated into its chromosome?

A)Lysogenic
B)Temperate
C)Prophage
D)Lytic
E)Lysogen

Answer 1

E

Question 2

The cellular complexes GroES and GroEL are involved in the assembly of the $\lambda$ phage virion.Which of the following describes their function during assembly?

A)They package the viral genome into the head.
B)They act as chaperones in the formation of the portal vertex.
C)They act as a scaffold for the assembly of the tail.
D)They acts as a scaffold for the assembly of the head.
E)The cleave concatemers of the viral genome during assembly.

Answer 2

They act as chaperones in the formation of the portal vertex.

Question 3

How does the binding of the $\lambda$ phage cI repressor to O_R1 and O_R2 block transcription from P_R?

A)It prevents the RNA polymerase from transcribing down the gene.
B)It blocks binding of the RNA polymerase to the -10 and -35 sites on the promoter.
C)It terminates transcription at an earlier terminator.
D)It leads to the degradation of the RNA produced from P_R.
E)It activates a promoter that produces an antisense transcript.

Answer 3

It blocks binding of the RNA polymerase to the -10 and -35 sites on the promoter.

Question 4

How does the cro protein from $\lambda$ phage help to establish a lytic infection?

A)It inhibits the integrase enzyme.
B)It activates the excision enzyme.
C)It binds to O_L1 and blocks transcription from P_L
D)It binds to O_R1 and blocks transcription from P_R
E)It binds to O_R3 and blocks transcription from P_RM.

Question 5

When bacterial cells that have an integrated $\lambda$ prophage in their genomes are treated with UV light,it leads to cleavage of the cI repressor.Which of the following host cell proteins activates the autoprotease activity of the cI repressor?

A)DNA excision repair enzyme
B)LexA
C)RecA
D)GroES
E)Exonuclease III

Question 6

The R and S proteins from $\lambda$ phage can form complexes called holin and spanin.Which of the following describes the process that these complexes participate in?

A)Assembly of the virion.
B)Replication of the viral genome.
C)Packaging of the viral genome into the head
D)Excision of the viral genome from the host chromosome.
E)Lysis of the host cell to release virions.

Question 7

The $\lambda$ phage will lysogenize the host cell if which of the following proteins is produced in sufficient levels during infection?

A)N
B)CI
C)Q
D)Integrase
E)Cro

Question 8

What is the function of the cII protein from $\lambda$ phage?

A)It represses transcription from P_R.
B)It activates transcription from P_RM.
C)It activates transcription from P_RE.
D)It inhibits cellular proteases that cleave the cI repressor.
E)It antiterminates transcription at t_L1.

Question 9

Why is binding of the $\lambda$ phage cI repressor to O_R1 and O_R2 necessary for transcription from P_RM?

A)It facilitates binding of the RNA polymerase to P_RM.
B)It blocks transcription from P_L which competes for the RNA polymerase.
C)It prevents transcription of an antisense RNA.
D)It stabilizes the transcript from P_RM.
E)It allows read through a transcriptional terminator.

Question 10

What is the function of the Int protein from $\lambda$ phage?

A)It mediates site specific recombination between attP and attB.
B)It ligates the ends of the viral chromosome.
C)It binds to multiple sites within the origin or replication.
D)It recruits the cellular DNA replication enzymes to the viral genome.
E)It acts as a scaffolding protein for virion assembly.

Question 11

The N and Q proteins from $\lambda$ phage both have which of the following functions?

A)Recombination of the viral genome
B)Repressors of transcription initiation
C)Activators of transcription initiation
D)Repressors of transcription termination
E)Unwinding of the viral genome

Question 12

What is the function of the cos sites in the $\lambda$ phage genome?

A)They function as the origin of DNA replication
B)They bind to the cI repressor
C)They bind to the N antiterminator
D)They circularize the genome
E)They are the sites of integration with the host chromosome

Question 13

The cI repressor of the $\lambda$ phage binds to several locations on the viral genome.Which of the following is the term that describes these binding sites?

A)Operators
B)Cos sites
C)Promoters
D)Terminators
E)AttP sites

Question 14

Which of the following statements about the transcripts from $\lambda$ phage that terminate at the transcriptional terminators t_L1 and t_R1 is FALSE?

A)They are expressed at immediate-early times.
B)The encode the proteins N and cro.
C)They are expressed first in the transcriptional program.
D)They contain NUT sequences.
E)They can be antiterminated by the Q protein.

Question 15

The Q protein from $\lambda$ phage activates expression of head and tail genes using which of the following mechanisms?

A)It causes anti-termination at the transcriptional terminator t_L1
B)It activates transcription from P_R'.
C)It causes anti-termination at the transcriptional terminator t_R'.
D)It inhibits activity of the N protein.
E)It inhibits the activity of the $\lambda$ cI repressor.

Question 16

Which of the following terms describes a bacteriophage that can either produce new virus particles or exist as a repressed integrated viral genome?

A)Lysogenic
B)Temperate
C)Prophage
D)Lytic
E)Lysogen

Question 17

Which of the following describes the function of the H protein,sometimes known as the tape measure,during assembly of the $\lambda$ virion?

A)It controls the amount of viral DNA packaged into the head.
B)It controls the length of the tail.
C)It controls the size of the head.
D)It cleaves the viral DNA and produces the cos sites.
E)It attaches the tail to the head.

Question 18

DNA replication of the genome of the $\lambda$ phage takes place through a rolling circle mechanism.Which of the following describes the products of this type of DNA replication?

A)Individual circular dsDNA genomes.
B)Individual linear dsDNA genomes.
C)Concatemers of dsDNA genomes.
D)Individual circular ssDNA genomes.
E)Individual linear ssDNA genomes.

Question 19

Retroregulation limits expression of the Int protein during lytic growth.The mechanism of retroregulation involves which of the following?

A)Binding of an antisense RNA that inhibits translation of the int mRNA.
B)Degradation of the Int protein by cellular proteases.
C)Inhibition of transcription from Pint.
D)Specific degradation of the int mRNA by Exonuclease III.
E)Termination of transcription upstream of the int coding region.

Question 20

In order to transcribe the late structure genes found on the left hand side of the $\lambda$ phage genome,which of the following must occur?

A)The phage genome must be integrated into the host chromosome.
B)The phage genome must be linear.
C)The phage genome must be circularized
D)The phage genome must be replicated into many copies.
E)The phage genome must be ligated into concatmers.

Question 21

When $\lambda$ phage infects E.coli cells that are metabolically active and in the logarithmic phase of growth,the virus will go lytic in most of the cells that it infects.

Question 22

If a $\lambda$ phage lysogen were superinfected with the same strain of $\lambda$ phage,the cI repressor would inhibit lytic replication from the incoming phage genome.

Question 23

The $\lambda$ phage immediate-early proteins N and cro are expressed only when the virus lysogenizes the host cell.

Question 24

Explain how the binding affinity of the $\lambda$ phage cI repressor to the three rightward operators (O_R1,O_R2,O_R3)controls transcription from both P_R and P_RM?

Question 25

Explain the mechanisms by which treatment of a $\lambda$ phage lysogen with UV light leads to the induction of the prophage and the production of virus particles.

Question 26

CRISPR elements are places in the bacterial chromosome where phage genomes integrate during lysogeny.

Question 27

The cIII protein from $\lambda$ phage inhibits cellular proteases that would degrade the cII protein.

Question 28

When there are high levels of the cI repressor of $\lambda$ phage then both P_R and P_RM are at maximal levels of transcription.