Figure 4.

Processed pseudogenes grouped according to their nucleotide sequence divergence from the parent RP protein. The distances have been calculated using MEGA [28]. The distance is a measure of the number of nucleotide substitutions per site. For mouse and rat, the distances have been scaled by decreasing it by a factor of three based on the reported observation that a threefold-higher rate of base substitution in neutral DNA is found along the rodent lineage when compared with the human lineage [20].