FIG. 3.

Frequency (a) and rate (b) of mutations in V regions and the entire env region. Clonally related sequences are shown by overlapping columns, with V region mutations in black and total mutations in grey. Switch variants are segregated into rapid (242 and JR-CSF) and slow (ADA and BaL) to reflect the timing shown in Fig. 1. Mutations in provisional isolates are indicated by lighter fill. The expected mutation rate (*) is taken from the work of Mansky and Temin (36). The mean number of V region mutations ± standard errors of the mean (excluding the provisional switch mutants) is shown by the horizontal bar and box, and the total mutations ± standard errors of the mean is shown by the filled black circle and vertical bar.