Fig. 2.
Estimated age of p53 site-containing ERV families. Insertion time of individual families of ERV LTRs is estimated by three methods. (A) Age of each LTR family, estimated by examining the presence of sequences in different species. 0 indicates no homologous hit, and 1 indicates that there are homologous hits. (B) Ages of near-complete ERVs, estimated by comparing their 5′ and 3′ LTR sequence divergence. Upper and lower bound were calculated by using a mutation rate of 2.3 × 10−9 and 5 × 10−9 substitutions per site per year, respectively. (C) Substitution rate, calculated by comparing individual fragments to the consensus by using the Jukes–Cantor formula (26). Fragments were grouped based on the presence of a p53 site and if they are solo LTRs, then the average and SD were calculated for each group. Branch length is taken from that of ref. 27.