FIG. 7.

Parameters of hypermutation in virus cultures. A total of 227 HIV-1 protease sequences, 131 of which were unique, were obtained from virus cultures. The unique sequences were compared for their distribution of percent A+T (A). Seventy-three were normal and 58 were hypermutated. (B) Distribution of G-to-A mutation in sequences from different culture conditions. Roman numerals refer to the culture conditions described in the legend to Fig. 6. Filled symbols, normal sequences; open symbols, hypermutated sequences. The cultures where abundant hypermutants covering the full range of G-to-A replacement were found are shaded. Below, the average ratio of percent G-to-A substitutions in the GA versus GG context is plotted for the sequences (all except six) in which both contexts were used. (C) Base composition of normal and hypermutated sequences from virus cultures. (D) Specificity for G-to-A substitutions in the GA or GG context in contrast to all other mutations, and the preferential use of GA over GG over the range of hypermutation.