ABSTRACT
Objective:To investigate the existence condition of hepatitis B surface antigen(HBsAg) termina-tion codon bias.Methods: A total of 174 reference sequences of all kinds of Hepatitis B virus(HBV) genotypes were chosen from GenBank,and compared by BioEdit.Then secondary structure of RNA was constructed and analyzed together.Results:(1) There were two types of HBsAg termination codon: TAA and TGA in 174 reference sequences.TAA was in 124 cases(71.26%);and TGA in 50 cases(28.74%).(2) There was codon bias selection in HBsAg termination codon,and it could affect the secondary structure of RNA and amino acid sequence encoding protein.Conclusion: HBsAg termination codon bias exists and may be related to RNA structure and the conservatiom of protein function in the evolutionary progress.