Sex chromosomal transposable element accumulation and male-driven substitutional evolution in humans

We sequenced the genomic region containing the human Y-linked zinc finger g ene (ZFY). Comparison of ZFY to the related region on the X chromosome (ZFX ) and to autosomal sequences reveals a significant accumulation of transpos able elements on the sex chromosomes. In addition, five times as many retro viruslike elements (RLEs) are present in the ZFY region as in the ZFX regio n. Thus, transposable elements accumulate more rapidly on the sex chromosom es, and the insertion of RLEs may occur more frequently in the male than in the female germ line. When the accumulation of substitutions in Alu elemen ts was analyzed, it was found that the Alu elements at the Y-chromosomal lo cus diverged significantly faster than those at the X-chromosomal locus, wh ereas the divergence of autosomal Alu elements was intermediate. The male-t o-female mutation rate ratio was estimated to be 2.5.