Figure 1.

Localization of the fission site within macaque BAC CH250-246c20 by FISH. (A) Ideograms showing cytogenetic manifestation of the fission of ancestral chromosome, represented by rhesus macaque chromosome 7, which created great ape chromosomes 15 and 14, here represented by the orangutan homologs (adapted from http://www.biologia.uniba.it/primates/). The red dots identify the location of the fission site region prior to the fission, and at 15qter and in 14q near the centromere immediately post-fission. This post-fission arrangement is grossly preserved in orangutan. (B) Chromosome locations of macaque BAC CH250-246c20 detected by FISH (red) pinpoint the fission site within its sequence and reveal post-fission rearrangements of the region in the hominids. The BAC hybridizes to rhesus macaque chromosome 7 (MMU), but produces two separate sets of signals in the chromosomes of all great apes except human. Chromosomes orthologous to human chromosomes 15, 14, and 4 are shown for orangutan (PAB), gorilla (GGO), chimpanzee (PTR), and human (HSA). FISH signals were not observed consistently with CH250-246c20 at any other chromosome locations in these species. See the text for explanations of the lack of signal from this BAC on the gorilla homolog of chromosome 14 and human and chimpanzee orthologs of chromosome 15. The double signals seen on some macaque chromatids, including those shown here, suggest that some of this BACs sequence might be duplicated around the centromere of macaque 7. MMU chr 7 refers to the chromosome number in the macaque karyotype. We use the chromosome numbering of the human karyotype for homologous chromosomes in gorilla, orangutan, and chimpanzee here and throughout this study.