Question
Identify the Virus based on the given cycle:
A. HIV
B. Hepatitis
C. Influenza
D. Herpes simplex
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Correct Answer » B Explanation |
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Ans. b. Hepatitis
The given lifecycle is of hepatitis B virus.
“HB V attachment to a receptor on the surface of hepatocytes occurs via a portion of the pre-S region of hepatitis B surface antigen (HBsAg). After uncoating of the virus, unidentified cellular enzymes convert the partially double- stranded DNA to covalent closed circular (ccc) DNA that can be detected in the nucleus. The cccDNA serves as the template for the production of HBV mRNAs and the 3.5-kb RNA pre-genome. The pre-genome is encapsidated by a packaging signal located near the 5′ end of the RNA into newly synthesized core particles, where it serves as template for the HBV reverse transcriptase encoded within the polymerase gene. An RNase H activity of the polymerase removes the RNA template as the negative-strand DNA is being synthesized. Positive-strand DNA synthesis does not proceed to completion within the core. resulting in replicative intermediates consisting of full-length minus-strand DNA plus variable-length (20-80%) positive-strand DNA. Core particles containing these DNA replicative intermediates bud from pre-Golgi membranes (acquiring HBsAg in the process) and may either exit the cell or reenter the intracellular infection cycle.” ,ivetz 27/e p501)
