<prompt> Which of the following HBV gene codes for HBeAg?PreCCSXC  <response>: Ans. a Pre CC Ref. Robbins pathology 7th 18-D; Ananthanarayan Microbiology, 7th 552HBV is a partially double-stranded deoxyribonucleic acid DNA virus packaged with a core protein HBcAg and DNA polymerase, and enclosed by envelope proteins HBsAg. Following receptor-mediated entry into hepatocytes, the virus enters the nucleus, where its DNA is frequently integrated into the host genome.The HBV has four genes: S, P, C, and X. The S gene codes for the major envelope protein HBsAg. The largest is P gene. It codes for DNA polymerase. The C gene codes for HBeAg and HBcAg. The C gene has a precore and a core region. If translation is initiated at the precore region, the protein product is HBeAg. If translation begins with the core region, HBcAg is the protein product. HBeAg is a marker of HBV replication and infectivity. The precore region is not necessary for viral replication. Precore mutants can replicate. They are readily detectable by HBV DNA in serum, but hepatitis B e antigen HbeAg is absent. The X gene codes for HBxAg. The product of the X gene is hepatitis B x antigen HBxAg. It may be involved in carcinogenesis. Basal core promoter mutants cause a reduction in HBeAg production.Protein synthesis proceeds from 4 open reading frames: Envelope proteins - Major, Middle, and Large - HBsAg from the -S gene, pre-Sl, and pre-S2 gene sequences; The e antigen HBeAg and core protein HBcAg from the -C gene and pre-C gene sequence; DNA polymerase protein from the -P gene; and Transactivator X-protein from the -X gene. 