Dead or just asleep? Variance of microsatellite allele distributions in the human Y-chromosome.

Several different methods confirm that a number of micro-satellites on the human Y-chromosome have allele distributions with different variances in different haplogroups, after adjusting for coalescent times. This can be demonstrated through both heteroscedasticity tests and by poor correlation of the variance vectors in different subclades. The most convincing demonstration however is the complete inactivity of some markers in certain subclades – “microsatellite death”, while they are still active in companion subclades. Many microsatellites have declined in activity as they proceed down through descendant subclades. This appears to confirm the theory of microsatellite life cycles, in which point mutations cause a steady decay in activity. However, the changes are too fast to be caused by point mutations alone, and slippage events may be implicated. The rich microsatellite terrain exposed in our large single-haplotype samples provides new opportunities for genotyping and analysis.