Chromosomal Rearrangements in Primates

Abstract

Abstract Primates are characterised by the non‐specialist nature of their morphological features that, together with the plasticity of their behaviours, have allowed them to exploit a wide variety of ecological niches. The study of the mechanisms involved in karyotype evolution in Primates is fundamental to our understanding of mammalian genome organisation and its role in adaptation. The combined use of comparative genomics and molecular cytogenetics has contributed to the finer dissection of chromosomal rearrangements in Primates, providing new insights into the dynamics of genome reshuffling that characterise this group. These approaches have permitted the characterisation of large‐scale genomic changes (i.e. inversions, fusions, fissions and translocations) as well as the chromosomal regions involved. This has contributed to refine Primate genomic architecture and evolutionary relationships among species. Here the different evolutionary patterns that have been described in Primates will be investigated together with the most plausible hypotheses for ancestral karyotypes that have been inferred for each specific lineage. Key Concepts Primates are classified into six major groups: lemurids, lorisids, tarsiers, New‐World monkeys, Old‐World monkeys and apes. The diversity of Primate species is exemplified by the variety of diploid numbers that characterise the group, ranging from 2n = 16 (i.e. Callicebus lugens ) to 2n = 72 (i.e. some Cercopithecus species). Comparative chromosomal studies among species are now possible, thanks to the combined use of different methodological approaches such whole‐genome comparative studies and FISH using either whole‐chromosome paintings or DNA‐specific probes. Chromosomal evolution within Primates is highly intricate, as each major taxonomic group has followed a different pattern of reorganisations. The family Hominidae, which includes orang‐utans, gorillas, chimpanzee and humans, has suffered few large‐scale chromosomal reorganisations since their common ancestor, most of them being lineage‐specific inversions. Lesser apes are characterised by an extremely high rate of chromosomal reshuffling, including lineage‐specific fissions, fusions, inversions and translocations. The group Catarrhini shows a general pattern of moderate rate of chromosomal changes, whereas Platyrrhini represents a highly diverse group with diploid numbers ranging from 2n = 16 in Callicebus to 2n = 62 in Lagothrix , in which inter‐ and intra‐specific chromosomal reorganisations are abundant. The general view is that the putative karyotype of the last common ancestor of Primates consists of 50 chromosomes, with the following homologies with human chromosomes: 1, 2p‐q, 2q, 3/21, 4, 5, 6, 7b, 7a/16p, 8, 9, 10p, 10q, 11, 12a/22a, 12b/22b, 13, 14/15, 16q, 17, 18, 19p, 19q, 20, X and Y.