Ribosomal and human-homologous repeated DNA distribution in the orangutan (Pongo pygmaeus)

Abstract

The distributions of ribosomal (18s + 28s) DNA in the orangutan (Pongo pygmaeus) and lowland gorilla (Gorilla gorilla gorilla) have been investigated by hybridization in situ, and the results compared with the distribution of this DNA in man, the chimpanzee (Pan troglodytes), and the mountain gorilla (Gorilla g. beringei) and with the distribution of sequences homologous to human satellite DNAs in these species. In the orangutan all sites of ribosomal DNA also contain human-homologous repeated DNA (HHR-DNA), and only the Y chromosome contains HHR-DNA but no ribosomal DNA (rDNA). In man and the chimpanzee, all sites of rDNA also contain HHR-DNA, but there are autosomal sites containing HHR-DNA that do not contain rDNA. In the lowland gorilla, only two pairs of chromosomes contain rDNA, and one of these contains HHR-DNA. The distribution of rDNA in all these species can be derived from that in the orangutan by postulating the loss of rDNA following Robertsonian translocation, pericentric inversion, or terminal deletion. Evidence is cited indicating that, at least in man, sites containing satellite DNA, which do not contain rDNA, are routinely found in association with the nucleolus, and it is suggested that this association may indicate a functional relationship between rDNA and HHR-DNA in man and the hominoid apes.