Localization of human midisatellite and macrosatellite DNA sequences on chromosomes 1 and X in the great apes.

The mechanism of speciation has remained largely unresolved, and hominoid evolutionary history based on chromosome rearrangements has been continuously challenged. The recent availability of the human-derived chromosome 1-specific midisatellite (D1Z2) and chromosome X-specific macrosatellite (DXZ4) DNA sequence probes has prompted us to hybridize the aforementioned to the members of the hominoid clade (chimpanzee, gorilla, and orangutan), using the fluorescence in-situ hybridization technique. Inconsistencies in the hybridization pattern for the D1Z2 DNA probe in the great ape species suggests that changes in this sequence have apparently taken place during the evolutionary process. No hybridization signal was observed in the orangutan chromosome 1, suggesting that a homologous D1Z2 DNA sequence may not be present in its genome, or that the sequence may be altered, rendering itself undetectable by human-derived DNA probes. Homology in the hybridization patterns for the DXZ4 probe in all three ape species illustrates that the sequence is apparently conserved. Such hybridization data provide some level of phylogenetic information on the recent ancestry of higher primates.