Sequence variation in ZFX introns in human populations

DNA variation in human populations was studied by examining the last intronof the ZFX gene (about 1, 151 bp) with a worldwide sample of 29individuals. Only one polymorphic site was found, which is located in anAlu sequence. This polymorphism is present at an intermediate frequency inall populations studied, and could be a shared polymorphism or due tomigration among populations in Asia, Europe, and Africa. The nucleotidediversity is 0.04%, supporting the view that the level of nucleotidevariation in nuclear DNA is very low in humans. From the sequence data, theage (T) of the most recent common ancestor of the sampled sequences isestimated: the mode of T is about 306,000 years, and the 95% confidenceinterval of T is 162,000-952,000 years. This mode estimate is considerablyolder than the estimates from Y- linked sequences.