FIG. 4.

Distribution of G-to-A mutations across the PLV genome. The frequency of G-to-A mutations was determined for each sequence position for gag, 5′ pol (PRT), 3′ pol (UI), and env as described in Materials and Methods. The nucleotide position for each gene is given on the x axis, and the y axis shows the number of sequences in which a G-to-A mutation arose at that position in the gene. The bracket in the panel showing the UI gene is immediately 3′ of the cPPT. The inverted bracket in PRT shows the region evaluated for nucleotide substitution in sequential FIVpco isolates.