Phylogenetic trees of env sequences from ΔGY-controllers. Trees excluded sequences with hypermutation, nonsense mutations, and frame-shifting length polymorphisms in env. Colors delineate time point, and shapes represent sequence types. The scale bar represents 1 nucleotide (nt), corresponding to p-distance of 0.0004. Because of small, in-frame deletions, the number of nucleotides analyzed for each tree differs slightly.