This set of Virology Multiple Choice Questions & Answers (MCQs) focuses on “Virus Latency”.
1. Which of the following viruses are best known for latent infections?
a) Rhinovirus
b) Herpesvirus
c) Poliovirus
d) HIV
View Answer
Explanation: Herpes virus is a group of viruses that are best known for latent infections. They infect a wide range of hosts including humans. Once the infection is established the virus remains associated with the host for the remainder of its life.
2. The bacteria carrying the phage DNA are called ________________
a) prophage
b) temperate phage
c) lysogens
d) bacteriophage
View Answer
Explanation: The bacteria which carry the phage DNA are called lysogens or lysogenic bacteria. It is a bacterial cell that can produce and transfer the ability to produce a phage.
3. The single-stranded regions in lambda phage are called _______________ sequences.
a) cro
b) cos
c) lox
d) cre
View Answer
Explanation: The single-stranded regions in lambda phage are called cos sequences. On infection, these sequences of 12 base pairs come together to form a circular DNA molecule which is covalently closed by the host DNA ligase enzyme.
4. Which of the following is a recombination site in the phage DNA?
a) att P
b) int
c) gal
d) lox
View Answer
Explanation: The recombination site in the phage DNA is the att P site. The position of the recombination site in the phage DNA lies downstream of the int gene and the region is referred to as att P site.
5. The critical component in the SOS response is ______________
a) Lex A
b) Rec A
c) Rec B
d) Lex B
View Answer
Explanation: The critical component in the SOS response is the Rec A protein. The main function of the Rec A protein is to mediate the recombination between DNA molecules. In the condition of stress, the Rec A protein alters its activity to become a specific protease.
6. LATs are _____________
a) introns
b) proteins
c) exons
d) fatty acids
View Answer
Explanation: LATs are latency-associated transcripts which are stable introns, produced by splicing of longer RNAs, and they do not encode proteins. The cells expressing LATs suppress the production of immediate early mRNAs.
7. The delayed infection of EBV causes _____________
a) glandular fever
b) swelling
c) pain
d) lesions
View Answer
Explanation: Epstein-Baar Virus (EBV) causes sub-clinical infection in infants and if the infection is delayed until adulthood, infectious mononucleosis or glandular fever results. It lasts for 2 to 3 weeks.
8. The primary acute infection caused by HSV-1 is _____________
a) chicken-pox
b) genital lesions
c) stomatitis
d) glandular fever
View Answer
Explanation: The primary acute infection caused by HSV-1 is stomatitis. It also causes infection of the mouth and tongue. Upon reactivation, it causes a cold sore. The site of latency for HSV-1 is the dorsal root ganglion of the trigeminal (cranial) nerve.
9. The site of latency for CMV is ____________
a) B cells
b) Salivary glands
c) Ganglion
d) Epithelium
View Answer
Explanation: The site of latency for Cytomegalovirus (CMV) is salivary glands and probably other sites. Cytomegalo refers to the characteristic swollen cell cytopathology caused by CMV to the cells of the kidney, lungs, and liver.
10. Temperate phage can adopt only the lytic or replication cycle.
a) True
b) False
View Answer
Explanation: Temperate phage is the bacteriophage that can adopt either lytic or lysogenic replication cycle. The phage DNA is inserted in the bacterial host genome during lysogeny and the phage in this state is called a prophage.
11. Rec A protein prevents the accumulation of cI protein.
a) True
b) False
View Answer
Explanation: Rec A prevents the accumulation of cI protein and hence only lytic replication cycle can occur even in cII protein is active. It also cleaves the cI protein.
Sanfoundry Global Education & Learning Series – Virology.
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