Abstract
Alu repetitive elements represent the largest family of short interspersed repetitive elements (SINEs) in humans as there are an excess of 500,000 copies per haploid genome. Of this, only a few thousand are thought to be polymorphic exhibiting both the insertion and lack of insertion alleles. The probability of independentAluinsertion events at the same site is remote. The ancestral state of anAlurepeat represents the absence of the insertion while the presence of an insertion, at a particular locus, is the derived state. In the present study, 1,533 unrelated individuals from 38 worldwide populations have been screened for a polymorphicAluelement using PCR technology with a novel pair of primers. ThisAluinsertion is located within intron G of the human progesterone receptor gene. Our results indicate that thisAlupolymorphic insertion is population specific since it is absent in most of the sub-Sahara African and Central/East Asian groups examined. Furthermore, this element is very rare in sub-Sahara Africa; hence, it may constitute the firstAlupolymorphism known to have resulted from a retroposition outside Africa subsequent to modern man migration out of Africa approximately 200,000 years ago. The low frequency of this insertion in Northern Asia and its absence in Central and South Asia may suggest that native American’s ancestors might have had contributions in their gene pool from Caucasian groups.