MOBILITY OF SHORT INTERSPERSED REPEATS WITHIN THE CHIMPANZEE LINEAGE

The PV subfamily of Alu repeats in human DNA is largely composed of re cently inserted members. Here we document additional members of the PV subfamily that are found in chimpanzee but not in the orthologous loc i of human and gorilla, confirming the relatively recent and independe nt expansion of this Alu subfamily in the chimpanzee lineage. As furth er evidence for the youth of this Alu subfamily, one PV Alu repeat is specific to Pan troglodytes, whereas others are present in Pan paniscu s as well. The A-rich tails of these Alu repeats have different length s in Pan paniscus and Pan troglodytes. The dimorphisms caused by the p resence and absence of PV Alu repeats and the length polymorphisms att ributed to their A-rich tails should provide valuable genetic markers for molecular-based studies of chimpanzee relationships. The existence of lineage-specific Alu repeats is a major sequence difference betwee n human and chimpanzee DNAs.