Identify the Virus based on the given cycle:
Ans. b. Hepatitis
The given lifecycle is of the hepatitis B virus.
- “HBV 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 covalently 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 a 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