A reassessment of the karyotype of Papio ursinus. Homoeology between human chromosome 15 and 22 and a characteristic submetacentric baboon chromosome.

The Giemsa-banded karyotype of the chacma baboon, Papio ursinus, was shown to be identical to that of Papio hamadryas. Comparison of G-banded P. ursinus (PUR) chromosomes with those of man (HSA) showed close morphological homoeology between PUR and HSA chromosomes 5, 8, 12, 19, and X, and partial homology for seven and 22 and was the only Papio chromosome containing a nucleolar organizer region (NOR). This baboon chromosome, therefore, shows genetic homoeology with human acrocentrics for a least 18S and 28S rRNA gene loci. It is postulated that HSA 15 and 22 originated from the fission of a larger submetacentric chromosome in a lower primate.