Chromosomal changes through pericentric inversions play an important role in the 
origin of species. Certain pericentric inversions are too minute to be detected 
cytogenetically, thus hindering the complete reconstruction of hominoid 
phylogeny. The advent of the fluorescence in situ hybridization (FISH) technique 
has facilitated the identification of many chromosomal segments, even at the 
single gene level. Therefore the cosmid probe for Prader-Willi (PWS)/Angelman 
syndrome to the loci on human chromosome 15 [q11-13] is being used as a marker 
to highlight the complementary sequence in higher primates. We hybridized 
metaphase chromosomes of chimpanzee (PTR), gorilla (GGO), and orangutan (PPY) 
with this probe (Oncor) to characterize the chromosomal segments because the 
nature of these pericentric inversions remains relatively unknown. Our 
observations suggest that a pericentric inversion has occurred in chimpanzee 
chromosome (PTR 16) which corresponds to human chromosome 15 at PTR 16 band 
p11-12, while in gorilla (GGO 15) and orangutan (PPY 16) the bands q11-13 
complemented to human chromosome 15 band q11-13. This approach has proven to be 
a better avenue to characterize the pericentric inversions which have apparently 
occurred during human evolution. "Genetic" divergence in the speciation process 
which occurs through "chromosomal" rearrangement needs to be reevaluated and 
further explored using newer techniques.