Question 1

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

Accepted Answer

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.F) C) and E)
G) A) and E)

Question 2

When bacterial cells that have an integrated  λ 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?

Accepted Answer

A)   DNA excision repair enzyme
B)   LexA
C)   RecA
D)   GroES
E)   Exonuclease IIIF) A) and B)
G) A) and C)

Question 3

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

Accepted Answer

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.F) A) and D)
G) B) and E)

Question 4

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

Accepted Answer

A) True 
 B)False  False

Question 5

How does the binding of the  λ phage cI repressor to OR1 and OR2 block transcription from PR?

Accepted Answer

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 PR.
E)   It activates a promoter that produces an antisense transcript.F) A) and C)
G) A) and E)

Question 6

Why is binding of the  λ phage cI repressor to OR1 and OR2 necessary for transcription from PRM?

Accepted Answer

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

Question 7

The λphage will lysogenize the host cell if which of the following proteins is produced in sufficient levels during infection?

Accepted Answer

A)   N
B)   CI
C)   Q
D)   Integrase
E)   CroF) A) and E)
G) C) and D) B

Question 8

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

Accepted Answer

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.F) A) and B)
G) B) and E)

Question 9

How does the cro protein from λ phage help to establish a lytic infection?

Accepted Answer

A)   It inhibits the integrase enzyme.
B)   It activates the excision enzyme.
C)   It binds to OL1 and blocks transcription from PL
D)   It binds to OR1 and blocks transcription from PR
E)   It binds to OR3 and blocks transcription from PRM.F) A) and C)
G) A) and B)

Question 10

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

Accepted Answer

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

Question 11

The cIII protein from  λ phage inhibits cellular proteases that would degrade the cII protein.

Accepted Answer

A) True 
 B)False

Question 12

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

Accepted Answer

A)   Lysogenic
B)   Temperate
C)   Prophage
D)   Lytic
E)   LysogenF) B) and E)
G) A) and C)

Question 13

Which of the following statements about the transcripts from  λ phage that terminate at the transcriptional terminators tL1 and tR1 is FALSE?

Accepted Answer

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.F) B) and C)
G) A) and C)

Question 14

Explain how the binding affinity of the λ phage cI repressor to the three rightward operators (OR1, OR2, OR3)controls transcription from both PR and PRM?

Accepted Answer

The l phage cI repressor binds to the th...

Question 15

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

Accepted Answer

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.F) C) and D)
G) B) and E)

Question 16

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

Accepted Answer

A) True 
 B)False

Question 17

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

Accepted Answer

A) True 
 B)False

Question 18

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

Accepted Answer

Treatment of host cells with UV light induces the SOS gene pathway, which serves to repair damage in the cellular genome.The expression of the SOS genes is normally inhibited by the cellular LexA repressor.Induction of the SOS genes requires activation of the "co-protease" activity of the RecA protein, which enhances the autoprotease activity of the LexA repressor.The LexA repressor cleaves itself into two domains, which inactivates is repressor activity and allows the SOS genes to be expressed.In addition to activating the autoprotease activity of the LexA protein, RecA can also activate a similar activity in the  λ repressor cI.This leads to the cleavage of cI into two domains.Inactivation of cI removes the repressor from the operators and activates the expression from PR and PL, which allows the lytic growth program to begin.

Question 19

When there are high levels of the cI repressor of  λ phage then both PR and PRM are at maximal levels of transcription.

Accepted Answer

A) True 
 B)False

Question 20

What is the function of the Int protein from λ phage?

Accepted Answer

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.F) D) and E)
G) A) and E)

Exam 8: Bacteriophage Lambda

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

Correct Answer
verified

When bacterial cells that have an integrated λ 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?

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified
False

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

Correct Answer
verified

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

Correct Answer
verified

The λphage will lysogenize the host cell if which of the following proteins is produced in sufficient levels during infection?

Correct Answer
verified
B

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

Correct Answer
verified

How does the cro protein from λ phage help to establish a lytic infection?

Correct Answer
verified

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

Correct Answer
verified

The cIII protein from λ phage inhibits cellular proteases that would degrade the cII protein.

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified
The l phage cI repressor binds to the th...
View Answer

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

Correct Answer
verified

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

Correct Answer
verified

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

Correct Answer
verified

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

When there are high levels of the cI repressor of λ phage then both P_Rand P_RM are at maximal levels of transcription.

Correct Answer
verified

What is the function of the Int protein from λ phage?

Correct Answer
verified

Exam 8: Bacteriophage Lambda

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

Correct AnswerverifiedShow Answer

When bacterial cells that have an integrated λ 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?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedFalse

How does the binding of the λ phage cI repressor to OR1 and OR2 block transcription from PR?

Correct AnswerverifiedShow Answer

Why is binding of the λ phage cI repressor to OR1 and OR2 necessary for transcription from PRM?

Correct AnswerverifiedShow Answer

The λphage will lysogenize the host cell if which of the following proteins is produced in sufficient levels during infection?

Correct AnswerverifiedB

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

Correct AnswerverifiedShow Answer

How does the cro protein from λ phage help to establish a lytic infection?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

The cIII protein from λ phage inhibits cellular proteases that would degrade the cII protein.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Which of the following statements about the transcripts from λ phage that terminate at the transcriptional terminators tL1 and tR1 is FALSE?

Correct AnswerverifiedShow Answer

Explain how the binding affinity of the λ phage cI repressor to the three rightward operators (OR1, OR2, OR3)controls transcription from both PR and PRM?

Correct AnswerverifiedThe l phage cI repressor binds to the th...View AnswerShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

When there are high levels of the cI repressor of λ phage then both PR and PRM are at maximal levels of transcription.

Correct AnswerverifiedShow Answer

What is the function of the Int protein from λ phage?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
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Correct Answer
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Correct Answer
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False

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

Correct Answer
verified

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

Correct Answer
verified

Correct Answer
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B

Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Correct Answer
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Which of the following statements about the transcripts from λ phage that terminate at the transcriptional terminators t_L1 and t_R1 is FALSE?

Correct Answer
verified

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

Correct Answer
verified
The l phage cI repressor binds to the th...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

When there are high levels of the cI repressor of λ phage then both P_Rand P_RM are at maximal levels of transcription.

Correct Answer
verified

Correct Answer
verified