Fig. 1.

Calculation of the ratio of nonsynonymous to synonymous G↔ A changes in a hypothetical HIV-1 gene. (a) NS/S G-to-A changes for Gs within the hA3G target motif TGGG and NS/S A-to-G changes for As within the hA3G product motif TAGG. (b) NS/S G-to-A changes for all Gs (random G) and NS/S A-to-G changes for all As (random A). The NS/S calculations of target and product motifs are shown below and above the hypothetical sequence in panel a, respectively. The NS/S calculations of all Gs and all As are shown below and above the hypothetical sequence in panel b, respectively. The codons are indicated by brackets.