F. Yang, E. Z. Alkalaeva, P. L. Perelman, A. T. Pardini, W. R. Harrison, P. C. M. O"Brien, B. Fu, A. S. Graphodatsky, M. A. Ferguson-Smith, and also T. J. Robinson

Edited by Joseph G. Gall, Carnegie institution of Washington, Baltimore, MD, and also approved November 19, 2002 (received for testimonial September 12, 2002)



Although our comparative chromosome painting technique failed to recognize unique characters that hold together the Afrotheria come the exemption of other placental groups, over there are nevertheless two adjacent segment combinations detected in the Afrotheria that are specifically noteworthy. The association of Hsa 10p/12/22qdist found in the aardvark chromosome 4q and also elephant chromosome 4 is present in the Carnivora (33–35) and has been suggested to comprise part of the genealogical carnivore karyotype (27). Clearly, the detection in the Afrotheria offers greater credence come the idea that it might be genealogical for every eutherian mammals. The Hsa 1/19p association detected in both the elephants and also aardvark has likewise been found in the galago (Otolemur crassicaudatus, ref. 31), and it also is likely to be ancestral for all eutherians. Should this hold, elephant chromosomes 2 and also 19 deserve to be derived from the aardvark chromosome 3q via one fission.

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Taking the results from the two Afrotherian orders, the Tubulidentata and Proboscidea, together with those derived from to represent of the other nine mammalian orders for which person chromosome-specific painting probes have been provided in cross-species in situ hybridization experiments leads us to propose the the eutherian genealogical karyotype made up 2n = 44, XY (Fig. 5). The 2n = 44 different from the 2n = 50 propose by Murphy et al. (27) and also the 2n = 48 by Chowdhary et al. (26). In big part, this needs to do v the configuration of chromosomes 1 and also 7 in our plan where the previous chromosome is represented by 3 independent aspects (1p-q, 1qt, and 19) in Murphy et al. (27) and the latter by 2 (10p, and also 12p-q, 22qt). These three fusions would certainly account because that the difference in between 2n = 50 and the 2n = 44 hypothesized herein. Distinctions with the Chowdhary et al. (26) proposal are more extensive.


Our data suggest the following human chromosomes, chromosome arms, and segmental associations to be embodied in this genealogical state. First, ripe chromosomes show finish chromosomal synteny, i.e., they room conserved in toto: Hsa5–6, Hsa9, Hsa11, Hsa13, Hsa17–18, Hsa20, and HsaX. Second, over there are six chromosomes that show conservation as single chromosome eight or block that happen on two different chromosomes in the ancestor: Hsa7a, Hsa7b, Hsa2q, Hsa2p, Hsa8q, and Hsa10q. Finally, over there are seven neighbor-joining combinations (i.e., the synteny is preserved in the majority of varieties of the assignment studied hence far but which correspond to 2 chromosomes in humans): Hsa1/19p, Hsa8p/4, Hsa3/21, Hsa15/14, Hsa10p/12pq/22q, Hsa19q/16q, and Hsa12qdis/22qdis). The evolution breakpoints identified by the genealogical karyotype carry out a departure point for addressing an essential questions in mammalian genome architecture. These encompass a feasible correlation with chromosomal polymorphisms or translocations that reason neoplasia in humans and also whether sequence analysis of the evolution breakpoints save on computer motifs the promote chromosome breakage (36).

In conclusion, although ours data execute not confirm the monophyly the the Afrotheria, that is notable that, included to the aardvark"s mix of look at plesiomorphic and also highly autapomorphic traits (37), we can include the retention that a karyotype that provides strong evidence that the eutherian genealogical state. Expanding comparative chromosome painting analyses to the remaining Afrotheria and also the Xenarthra, the two basal superordinal teams at the root of the eutherian phylogenetic tree, will facilitate the carry of mapping data among evolutionarily very divergent species and add to the breakthrough of a cohesive, chromosomal character-based phylogenetic frame for all eutherian mammals.

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Acknowledgments

We room grateful to Johan Watson (Free State department of Environmental and also Economic Affairs) for permission to collect aardvark material and also for help in the field, and to Dr. D. Suwattana (Chulalongkorn University, Bangkok, Thailand) because that metaphase chromosome cabinet suspensions the the oriental elephant. This research was sponsor in component by a Wellcome to trust Collaborative research Initiative grant (to T.J.R. And M.A.F.-S.), the southern African nationwide Research foundation (to T.J.R.), the National natural Science structure of China and the Chinese Academy of scientific researches (to F.Y.), the Russian money of simple Research (to A.S.G., P.L.P., and also E.Z.A.), and Grant 01-2163 from the global Association for the promo of Co-operation with scientists from the new Independent claims of the former Soviet Union (to A.S.G. And M.A.F.-S.).