[Nucleotide frequency analysis of bacteriophage phi X174 genome]

Detailed analysis was carried out on the nucleotide frequencies in the genome of bacteriophage phi X174. In coding regions the distribution of four nucleotides at the three codon sites was highly non-random, and the patterns were conspicuously similar among the genes, implying that it might be a feature of the genome. An index c, which was based on the chi 2 statistics of the site by base 3 x 4 table, was introduced to reveal he extra information embedded in the coding region, and also to discriminate between coding and non-coding open reading frames. Doublet deviation analysis showed that deviation patterns were not significantly related to the codon sites in coding regions, and were also very similar in different genes. Possible mechanisms of such similarity are discussed.