Divergent human Y-chromosome microsatellite evolution rates

In this work, we analyze several characteristics influencing the low variab ility of the microsatellite DYS19 in the major founder Amerindian Y chromos ome lineage containing the paint mutation DYS199-T. Variation of DYS19 was compared with Chat of five other Y-linked tetranucleotide repeat loci (DYS3 89A, DYS389B, DYS390. DYS391, and DYS393) in the DYS199-T lineage. All the other microsatellites showed significantly higher levels of variability tha n DYS19 as measured by gene diversity and repeat number variance. Moreover, we had previously shown Chat DYS19 had high diversity in Brazilians and in several other populations worldwide. Thus, the slow DYS19 evolution in the DYS199-T lineage seems to be both locus and allele specific, To understand the slow DYS19 evolutionary rate, the microsatellite loci were compared ac cording to their mapping on the Y chromosome and also on the basis of struc tural aspects such as the base composition of the repeat motif and flanking regions and the degree of perfection and size (repeat number) of the varia ble blocks. The only observed difference that might be related to the low D YS19 variability is its small average number of repeats, a value expected t o be closer to the founder DYS19 allele in the DYS199-T lineage. These data were also compared to other derived Y lineages. The Tat-C lineage displaye d a lower DYS19 variability correlated to a small average repeat number, wh ile in the DYS234-G lineage, a high DYS19 variability was found associated to a larger average repeat number. This approach reveals Chat evolution of Y microsatellites in Lineages defined by slowly evolving markers, such as p oint mutations, can be greatly influenced by the size (number of repeats of the variable block) of the founder allele in each microsatellite locus. Th us lineage-dating methods using microsatellite variation should be practice d with great care.