Reconstruction Of Primate Karyotype Evolution

The Ancestral Primate Karyotype

Because chromosomal homology maps between human and approx 30 nonprimate mammals and more than 50 primates have been established, the data set available provides a firm basis on which proposals for common ancestral mammalian chromosomal traits and shared derived primate-specific chromosome forms can be made. For the sake of clarity and simplicity, in the following sections chromosomes are always numbered according to their human homologous counterparts.

When comparing the karyotypes of species from different placental mammalian orders, a surprisingly high degree of conservation can be observed for the majority of species. The homologs of human autosomes 1, 5, 6, 9, 11, 13, 17, 18, and 20 are found conserved as separate entities in several different orders and are therefore assumed to represent ancestral mammalian chromosome forms. In addition, human chromosome 3, 4, 14, 15, and 21 homologs are entirely conserved in other mammalian orders, however, translocated. Syntenic associations of human homologous chromosomes 3/21, 4/8p, and 14/15 are, therefore, also considered to be ancestral for placental mammals. Human chromosome 2, 7, 8, 10, 16, and 19 homologs are found split in two separate syntenic segments, some of them are associated with further chromosomal material. Human chromosome 2 is a fusion product of two separate ancestral homologs 2pter-q13 (2a) and 2q13-qter (2b). Human chromosome 7 is a complex fusion product of

Ancestral mammalian karyotype (2n=46)

Ancestral primate karyotype (2n=50)

Ancestral mammalian karyotype (2n=46)

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