Microbiology An Evolving Science 4th Edition By Foster – Test Bank

CHAPTER 11: Viral Molecular Biology

MULTIPLE CHOICE

1.Which of the following statements is FALSE regarding phage lambda as a temperate phage?

a. The genome of phage lambda integrates into the genome of the host cell and becomes a prophage.

b. The phage DNA replicates as an integrated prophage but does not produce phage particles.

c. Lambda phage immediately kills its host after infection.

d. The presence of the lambda prophage confers resistant to new infections by lambda.

e. Incorporation of lambda phage DNA into the bacterial genome is called lysogeny.

ANS:CDIF:EasyREF:11.1

OBJ: 11.1a Outline the experiments that led to the discovery of phage lambda

MSC:Remembering

2.What is the cause for cloudy centers appearing in lambda plaques on an Escherichia coli confluent plate?

a. A low multiplicity of infection prevents the appearance of large numbers of lysed cells.

b. Cell debris forms a physical barrier between uninfected cells and virions.

c. Compounds in agar or nutrient medium protect bacterial cells from infection.

d. A large number of infected cells become resistant to bacteriophage infection.

e. Some infected cells become lysogens and start growing up where the infection began.

ANS:EDIF:EasyREF:11.1

OBJ: 11.1a Outline the experiments that led to the discovery of phage lambda

MSC:Understanding

3.The lambda genome is replicated by a rolling circle mechanism. What is the end result after a round of replication?

a. a single-stranded DNA that is immediately packaged in the phage head

b. two molecules resulting from a step of circle-to-circle replication

c. several circular molecules inserted into each other; the circles are cleaved at the cos sites and eventually relegated

d. a concatemer (i.e., multiple genomes joined end to tail, which are cleaved at cos sites by a terminase), producing linear double-stranded DNA prior to packaging

e. several Okazaki fragments that are subsequently ligated

ANS:DDIF:MediumREF:11.1

OBJ: 11.1b List the structures present in phage lambda and describe the function of each structure

MSC:Understanding

4.The capsid of the bacteriophage lambda is composed of two types of protein subunits, namely, D and E, arranged in a(n)________ shape.

a. icosahedral d. triclinic

b. rhomboidal e. cubic

c. pyramidal

ANS:ADIF:EasyREF:11.1

OBJ: 11.1b List the structures present in phage lambda and describe the function of each structure

MSC:Remembering

5.Which of the following is FALSE regarding the establishment of lysogeny?

a. Lambda phage DNA integrates as a prophage in the host genome at the att site by site-specific recombination.

b. Rolling-circle replication generates multiple genomes in tandem, which are eventually cleaved by the enzyme terminase.

c. Production of the repressor CI by the integrated prophage prevents superinfection by other lambda phages.

d. A CI lambda repressor dimer binds to the major groove of a specific DNA sequence in the bacterial host, preventing the transcription of lytic promoters.

e. Once integrated in the host’s DNA, gene expression from the prophage is limited to a few proteins, including the repressor C1.

ANS:BDIF:DifficultREF:11.1

OBJ: 11.1c Categorize the E. coli host proteins required for phage lambda attachment and infection

MSC:Understanding

6.Control proteins Cro and CII lead to lysis or lysogeny, respectively. What environmental signal in the host contributes to regulate the amount of CII by influencing the activity of the protease HflB?

a. Mg2 ion concentrations d. nutrient concentrations

b. temperature e. helper phages

c. water availability

ANS:DDIF:EasyREF:11.1

OBJ: 11.1d Describe the molecular regulation of the switch from lysogenic to lytic growth

MSC: Applying

7.The figure below shows a partial map (0 to about 22 kbp) of the lambda DNA genome. Which gene or gene set is mislabeled?

a. A–lysis/lysogeny switch d. D–tail tip

b. B–head e. E–tail fibers

c. C–tail

ANS:ADIF:DifficultREF:11.1

OBJ: 11.1b List the structures present in phage lambda and describe the function of each structure | 11.1d Describe the molecular regulation of the switch from lysogenic to lytic growth

MSC:Understanding

8.The figure below shows a partial map of the lambda DNA genome (2348 kb). The early left and right operons as well as the late operon are indicated. Which gene or gene set is mislabeled?

a. A–integration to host chromosome d. D–lysis

b. B–lysis/lysogeny switch e. E–terminase

c. C–DNA replication

ANS:EDIF:DifficultREF:11.1

OBJ: 11.1b List the structures present in phage lambda and describe the function of each structure | 11.1d Describe the molecular regulation of the switch from lysogenic to lytic growth

MSC:Understanding

9.Which host protein cleaves CI and triggers up to 100% lysis after lysogenic Escherichia coli cells are exposed to ultraviolet light?

a. primase d. terminase

b. DNA polymerase III e. Lon protease

c. RecA

ANS:CDIF:MediumREF:11.1

OBJ: 11.1d Describe the molecular regulation of the switch from lysogenic to lytic growth

MSC:Understanding

10.The genome of the influenza virus is best described as

a. () strand segmented RNA. d. () strand single-piece RNA.

b. () strand segmented RNA. e. double-stranded RNA.

c. () strand single-piece RNA.