Physical mapping of human 7q and 14q subtelomeric DNA sequences in the great apes

Phylogenetic divergence of the members of the Pongidae family has been based on genetic evidence. The terminal repeat array (T2AG3) has lately been considered as an additional basis to analyze genomes of highly related species. The recent isolation of subtelomeric DNA probes specific for human (HSA) chromosomes 7q and 14q has prompted us to cross-hybridize them to the chromosomes of the chimpanzee (PTR), gorilla (GGO) and orangutan (PPY) to search for its equivalent locations in the great ape species. Both probes hybridized to the equivalent telomeric sites of the long (q) arms of all three great ape species. Hybridization signals to the 7q subtelomeric DNA sequence probe were observed at the telomeres of HSA 7q, PTR 6q, GGO 6q and PPY 10q, while hybridization signals to the 14q subtelomeric DNA sequence probe were observed at the telomeres of HSA 14q, PTR 15q, GGO 18q and PPY 15q. No hybridization signals to the chromosome 7-specific alpha satellite DNA probe on the centromeric regions of the ape chromosomes were observed. Our observations demonstrate sequence homology of the subtelomeric repeat families D7S427 and D14S308 in the ape chromosomes. An analogous number of subtelomeric repeat units exists in these chromosomes and has been preserved through the course of differentiation of the hominoid species. Our investigation also suggests a difference in the number of alpha satellite DNA repeat units in the equivalent ape chromosomes, possibly derived from interchromosomal transfers and subsequent amplification of ancestral alpha satellite sequences.