Brock Biology of MicroorganisMs
chapter 1-9 eXaM QUestions With
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1) You are attempting to mutate lambda to affect whether lysis or lysogeny
occurs after lambda infection. Which mutation would INCREASE the chances
of LYSOGENY over lysis?
A) deletion or inactivation of the cI gene
B) deletion or inactivation of the cro gene
C) overexpression of the cro gene
D) deletion of both the cro and cI genes - ANSWER ✓B) deletion or
inactivation of the cro gene
2) Regarding the viral membrane of an enveloped virus, the lipids are derived
from the ________, and the proteins are encoded by ________.
A) host's cell membrane / viral genes
B) virion / viral genes
C) host's cell membrane / host's genes
D) virion / host's genes - ANSWER ✓A) host's cell membrane / viral genes
3) Virions infecting some bacteria possess the enzyme ________ that makes a
small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
,A) peptidoglycanase
B) infectase
C) lysozyme
D) nuclease - ANSWER ✓C) lysozyme
4) The use of ________ is the easiest and most effective way of studying many
animal and plant viruses.
A) bacterial cultures
B) tissue or cell culture
C) live hosts
D) prophages - ANSWER ✓B) tissue or cell culture
5) When solutions of host cells and infectious virions are mixed and spread on
an agar plate, ________ form where viruses lyse the host cells.
A) insertion sequences
B) plaques
C) prophages
D) colonies - ANSWER ✓B) plaques
6) T4 genes are transcribed by host RNA polymerase, yet the transcription of
T4 genes is carefully controlled so that groups of T4 genes are transcribed at
specific times after infection. How is this accomplished?
A) Early T4 genes encode for proteolytic enzymes that destroy the host RNA
polymerase. Subsequently a viral polymerase is created that transcribes the
middle and late genes in the correct order.
B) Early and middle T4 genes encode for proteins that modify the activity of
sigma factors and host RNA polymerase to regulate the expression of T4 genes.
C) Each group of T4 genes has a different promoter that indicates that order in
which they should be transcribed in based on the affinity of the promoter for the
host RNA polymerase.
,D) Rolling circle replication of the viral genome ensures that the genes are
available for transcription in the correct order. - ANSWER ✓B) Early and
middle T4 genes encode for proteins that modify the activity of sigma factors
and host RNA polymerase to regulate the expression of T4 genes.
7) The T4 phage protects its DNA from host restriction endonucleases by
A) glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
B) methylating all four bases (A, T, C, G) in the T4 genome to prevent DNA
cleavage.
C) integrating the viral genome into the host genome where it will not be
degraded.
D) circularizing the viral genome so that it will not be degraded. - ANSWER
✓A) glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
8) In E. coli, the adenine in the sequence GATC is methylated by the Dam
enzyme. In the same cells a restriction endonuclease recognizes and cleaves
dsDNA with GATC on either strand. Why does E. coli have these two enzymes?
A) The enzymes cut the E. coli genome into pieces that bind to viral particles
and inhibit viral replication.
B) The enzymes increase the rate of mutation and genome rearrangement, thus
increasing the likelihood that E. coli cells will mutate and become resistant to
viral infection.
C) The enzymes encourage lysogeny because the cleavage sites are recognized
by viral integrases.
D) The enzymes protect E. coli from infection by preferentially degrading viral
or other exogenous DNA that is not methylated. - ANSWER ✓D) The enzymes
protect E. coli from infection by preferentially degrading viral or other
exogenous DNA that is not methylated.
9) Which of the following samples would contain the MOST genetic diversity?
A) viral metagenomes from the ocean
B) bacterial metagenomes from the ocean
, C) microbial eukaryotic metagenomes from the ocean
D) viral metagenomes from human red blood cells - ANSWER ✓A) viral
metagenomes from the ocean
10) Viral proteins are categorized as early, middle, and late. Early proteins
typically are necessary for
A) production of viral mRNA.
B) packaging of DNA into the nucleocapsid.
C) copying the viral genome.
D) production of viral mRNA and copying the viral genome. - ANSWER ✓D)
production of viral mRNA and copying the viral genome.
11) A cell that allows the complete replication cycle of a virus to take place is
said to be a
A) permissive host.
B) viral cell.
C) dead cell.
D) lytic cell. - ANSWER ✓A) permissive host.
12) In a natural population of diverse slow-growing prokaryotic cells, what
type of viruses would you expect to be most common?
A) lytic bacteriophages
B) enveloped viruses
C) icosahedral viruses
D) temperate bacteriophages - ANSWER ✓A) lytic bacteriophages
13) How do bacteriophage influence bacterial evolution?
A) Bacteriophage cause cleavage and rearrangement of bacterial genomes, thus
accelerating bacterial evolution.
chapter 1-9 eXaM QUestions With
correct solUtions|UpDateD 2025
syllaBUs|100% gUaranteeD
pass|a+ graDeD!!<<neWest
Version>>
1) You are attempting to mutate lambda to affect whether lysis or lysogeny
occurs after lambda infection. Which mutation would INCREASE the chances
of LYSOGENY over lysis?
A) deletion or inactivation of the cI gene
B) deletion or inactivation of the cro gene
C) overexpression of the cro gene
D) deletion of both the cro and cI genes - ANSWER ✓B) deletion or
inactivation of the cro gene
2) Regarding the viral membrane of an enveloped virus, the lipids are derived
from the ________, and the proteins are encoded by ________.
A) host's cell membrane / viral genes
B) virion / viral genes
C) host's cell membrane / host's genes
D) virion / host's genes - ANSWER ✓A) host's cell membrane / viral genes
3) Virions infecting some bacteria possess the enzyme ________ that makes a
small hole in the bacterial cell wall, allowing the viral nucleic acid to enter.
,A) peptidoglycanase
B) infectase
C) lysozyme
D) nuclease - ANSWER ✓C) lysozyme
4) The use of ________ is the easiest and most effective way of studying many
animal and plant viruses.
A) bacterial cultures
B) tissue or cell culture
C) live hosts
D) prophages - ANSWER ✓B) tissue or cell culture
5) When solutions of host cells and infectious virions are mixed and spread on
an agar plate, ________ form where viruses lyse the host cells.
A) insertion sequences
B) plaques
C) prophages
D) colonies - ANSWER ✓B) plaques
6) T4 genes are transcribed by host RNA polymerase, yet the transcription of
T4 genes is carefully controlled so that groups of T4 genes are transcribed at
specific times after infection. How is this accomplished?
A) Early T4 genes encode for proteolytic enzymes that destroy the host RNA
polymerase. Subsequently a viral polymerase is created that transcribes the
middle and late genes in the correct order.
B) Early and middle T4 genes encode for proteins that modify the activity of
sigma factors and host RNA polymerase to regulate the expression of T4 genes.
C) Each group of T4 genes has a different promoter that indicates that order in
which they should be transcribed in based on the affinity of the promoter for the
host RNA polymerase.
,D) Rolling circle replication of the viral genome ensures that the genes are
available for transcription in the correct order. - ANSWER ✓B) Early and
middle T4 genes encode for proteins that modify the activity of sigma factors
and host RNA polymerase to regulate the expression of T4 genes.
7) The T4 phage protects its DNA from host restriction endonucleases by
A) glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
B) methylating all four bases (A, T, C, G) in the T4 genome to prevent DNA
cleavage.
C) integrating the viral genome into the host genome where it will not be
degraded.
D) circularizing the viral genome so that it will not be degraded. - ANSWER
✓A) glucosylating cytosine bases in the T4 genome to prevent DNA cleavage.
8) In E. coli, the adenine in the sequence GATC is methylated by the Dam
enzyme. In the same cells a restriction endonuclease recognizes and cleaves
dsDNA with GATC on either strand. Why does E. coli have these two enzymes?
A) The enzymes cut the E. coli genome into pieces that bind to viral particles
and inhibit viral replication.
B) The enzymes increase the rate of mutation and genome rearrangement, thus
increasing the likelihood that E. coli cells will mutate and become resistant to
viral infection.
C) The enzymes encourage lysogeny because the cleavage sites are recognized
by viral integrases.
D) The enzymes protect E. coli from infection by preferentially degrading viral
or other exogenous DNA that is not methylated. - ANSWER ✓D) The enzymes
protect E. coli from infection by preferentially degrading viral or other
exogenous DNA that is not methylated.
9) Which of the following samples would contain the MOST genetic diversity?
A) viral metagenomes from the ocean
B) bacterial metagenomes from the ocean
, C) microbial eukaryotic metagenomes from the ocean
D) viral metagenomes from human red blood cells - ANSWER ✓A) viral
metagenomes from the ocean
10) Viral proteins are categorized as early, middle, and late. Early proteins
typically are necessary for
A) production of viral mRNA.
B) packaging of DNA into the nucleocapsid.
C) copying the viral genome.
D) production of viral mRNA and copying the viral genome. - ANSWER ✓D)
production of viral mRNA and copying the viral genome.
11) A cell that allows the complete replication cycle of a virus to take place is
said to be a
A) permissive host.
B) viral cell.
C) dead cell.
D) lytic cell. - ANSWER ✓A) permissive host.
12) In a natural population of diverse slow-growing prokaryotic cells, what
type of viruses would you expect to be most common?
A) lytic bacteriophages
B) enveloped viruses
C) icosahedral viruses
D) temperate bacteriophages - ANSWER ✓A) lytic bacteriophages
13) How do bacteriophage influence bacterial evolution?
A) Bacteriophage cause cleavage and rearrangement of bacterial genomes, thus
accelerating bacterial evolution.
