A polymorphic L1 retroposon insertion in the centromere of the human Y chromosome

We have identified a novel polymorphic L1 retroposon insertion, designated LY1, in the centromeric alphoid array of the human Y chromosome. The elemen t belongs to the transpositionally active Ta subset and its presence is com patible with normal centromere function. It was found at highest frequency in China, where it accounts for 23% of the Nan sample, and was present at l ow frequencies in the surrounding areas, but was not found at all outside A sia. Chromosomes carrying LY1 show considerable microsatellite diversity, s uggesting an ancient origin for the lineage at similar to 10 000 years ago (with wide confidence limits), but only limited subsequent migration.