Sequence variability of a human pseudogene

We have obtained haplotypes from the autosomal glucocerebrosidase pseudogen e (psGBA) for 100 human chromosomes from worldwide populations, as well as for four chimpanzee and four gorilla chromosomes. In humans, in a 5420-nucl eotide stretch analyzed, variation comprises 17 substitutions, a 3-bp delet ion, and a length polymorphism at a polyadenine tract. The substitution rat e on the pseudogene (1.23 +/- 0.22 x 10(-9) per nucleotide and year) is wit hin the range of previous estimates considering phylogenetic estimations. R ecombination within the pseudogene was recognized, although the low variabi lity of this locus prevented an accurate measure of recombination rates. At least 13% of the psGBA sequence could be attributed to gene conversion fro m the contiguous GBA gene, whereas the reciprocal event has been shown to l ead to Gaucher disease. Human psGBA sequences showed a recent coalescence t ime (similar to 200,000 yr ago), acid the most ancestral haplotype was foun d only in Africans; both observations are compatible with the replacement h ypothesis of human origins. In a deeper timeframe, phylogenetic analysis sh owed that the duplication event that created psGBA could be dated at simila r to 27 million years ago, in agreement with previous estimates.