Sequence variation and extent of sequence variability within individual sites of Gag and Env subtypes B and C. Histogram of gradients of dN/dS change for Gag p17 and p24 for subtype B (A) and subtype C (C). Env includes gp120, gp41, and variable loops for subtype B (E) and subtype C (G). Scatter plots of gradient and mean dN/dS values for subtype B of Gag p17 and p24 (B), subtype C of Gag p17 and p24 (D), subtype B of Env gp120, gp41, and variable loops (F), and subtype C of Env gp120, gp41, and variable loops (H). For panels A to H, the sites buried in the core of the protein (solvent accessibility values of <20) are shown in blue, and those exposed to solvent (solvent accessibility values of ≥20) in red. Variable loops (V1/V2 and V3) of gp120 are shown in green.