Y-chromosome-specific restriction fragment length polymorphisms (RFLPs): Relevance to human evolution and human variation

Abstract

The human Y chromosome comprises two distinct parts: the pseudoautosomal region on the tip of the short arm that pairs with the X chromosome in male meiosis and undergoes recombination, and the remainder of the chromosome, which is male‐specific and not involved in recombination. It is this haploid part of the Y chromosome, with its accumulation of mutations, that is of interest to human biologists because the variation within it potentially reflects the paternal line in human evolution (just as mtDNA analysis represents maternal lineages). The Y chromosome, however, appears to contain very few restriction fragment length polymorphisms (RFLPs), and furthermore, understanding of the polymorphic basis of some of these is presently imperfect. These latter problems include the possibility of multiple origins of the same allele, especially in repeat sequence polymorphisms, and failure to recognize the ancestral allele at a locus. All of these restrictions and difficulties mean that no comprehensive understanding of either Y chromosome evolution or its variability among the world's populations is yet possible. This report examines the current knowledge of Y‐chromosome population genetics obtained using probes such as p12f, p49a, pYAP, and pYαl, including their use in measuring gene flow and also in population histories and differentiation. Most studies have reported allele frequencies at a particular locus, but a fuller understanding of Y chromosome evolution and variation will require haplotype data. One interesting observation is the low diversity for some Y‐chromosome polymorphisms in African populations compared to Caucasoids, a contrast to the pattern seen for other DNA polymorphisms. The role of different mate choice systems in acting to substantially reduce Y‐chromosome variation is considered. © 1996 Wiley‐Liss, Inc.