Members of the recently inserted human-specific (HS)/predicted variant
(PV) subfamily of Alu elements were sequenced. A number of these Alu
elements share greater than 98% sequence identity with the subfamily c
onsensus sequence, and they are flanked by perfect 5' and 3' direct re
peats ranging in size from 6 to 15 nucleotides (nt). Based on the low
number of random mutations, the estimated average age of these element
s was calculated to be 1.5 million years (Myr). All the young Alu subf
amily members were restricted to the human genome, as judged by polyme
rase chain reaction (PCR) amplification of human and non-human primate
DNA samples using the unique flanking sequences specific for each Alu
element. The chromosomal locations of several Alu elements belonging
to the young subfamilies, designated as HS/PV and Sb2, were determined
by PCR amplification of DNA samples from human/rodent somatic cell hy
brid panels. A statistical analysis of the chromosomal distribution pa
ttern showed that the recently inserted Alu elements appear to integra
te randomly in the human genome.