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Microbiology Multiple Choice Questions on “Replication of Bacterial Viruses”.
1. Which of the following is the first step in replication by bacterial phages?
A. adsorption
B. penetration
C. transcription
D. assembly and release
Answer: A
Clarification: The first step in the infection of a host bacterial cell by a phage is adsorption. The infection of a host bacterial cell cannot occur without adsorption.
2. At what temperature incubation is required for the adsorption of phage T4 and DNA injection into E.coli?
A. 50 degree C
B. 15 degree C
C. 37 degree C
D. 80 degree C
Answer: C
Clarification: Phage T4 adsorption and DNA injection into E.coli spheroplasts require the phage particles to be incubated with spheroplasts at 37 degree C for 10 mins.
3. Which of the following is the correct sequence of events in replication by bacterial phage?
A. adsorption, pinning, DNA injection, sheath contraction
B. adsorption, pinning, sheath contraction, DNA injection
C. adsorption, absorption, sheath contraction, pinning
D. absorption, adsorption, DNA injection
Answer: B
Clarification: The first step in the process of replication by bacterial phage is adsorption to the host cell. This is followed by pinning when the tail pins attach to the cell surface. Then the sheath contracts driving the tail core into the cell through the cell membrane and then the virus injects its DNA into the cell.
4. The protein coat of the virus remains outside the host cell.
A. True
B. False
Answer: A
Clarification: The protein coat, which forms the phage head, and the tail structure of the virus remains outside the cell.
5. The delayed early genes codes for which of the following enzymes?
A. phage enzymes
B. RNA polymerase
C. nucleases
D. oxidases
Answer: A
Clarification: Delayed early genes code for phage enzymes which produce unique phage DNA constituents such as 5-hydroxymethylcytosines; which destroy precursors of cytosine deoxynucleotides so that no bacterial cytosine will be incorporated into phage DNA.
6. Which of the following enzymes transcribe late genes?
A. ligases
B. nucleases
C. RNA polymerase
D. restriction enzymes
Answer: C
Clarification: Delayed early genes code for second altered RNA polymerase that will transcribe the late genes.
7. In the growth curve of plaque-forming units, the time from infection until lysis is known as ____________________
A. eclipse period
B. rise period
C. burst period
D. latent period
Answer: D
Clarification: No newly released extracellular phages can be seen until lysis begins; the time from infection until lysis is the latent period.
8. What is the colour of the plaque formed?
A. yellow
B. opaque
C. clear
D. blue
Answer: C
Clarification: Growth of phage is indicated by the appearance of plaques that are clear zones, unlike the otherwise opaque growth of the host bacterium.
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