A REAPPRAISAL OF THE TANDEM FUSION THEORY OF KARYOTYPE EVOLUTION IN THE INDIAN MUNTJAC USING CHROMOSOME PAINTING

We have tested the tandem fusion hypothesis of the origin of the India n muntjac karyotype (2n = 6/7) by using reciprocal chromosome painting between the Indian muntjac, Chinese muntjac (n = 46) and brown brocke t deer (2n = 70 + 3B) with chromosome-specific paint probes derived fr om flow-sorted chromosomes of these three deer species. Our results ha ve shown that the euchromatic blocks of all chromosome arms of the bro wn brocket deer have been conserved apparently unchanged in number and content in the Indian muntjac. While confirming the conservation pn t ote of most of Chinese muntjac euchromatin in the karyotype of the Ind ian muntjac, we demonstrate that the synteny of chromosomes 1, 2, 3, 4 and 5 of the Chinese muntjac has been disrupted by chromosome rearran gements other than fusions. This indicates that the present karyotype of the Indian muntjac cannot be reconstructed from the hypothetical Ch inese muntjaclike 2n = 46 ancestral karyotype exclusively by chromosom e fusions. Furthermore, we have shown that the breakpoints of these re arrangements appear to have occurred near to the fusion points formed during the origin of the 2n = 46 karyotype of the Chinese muntjac from a 2n = 70 karyotype, which is believed to be ancestral for the family Cervidae. Moreover, we substantiate that on the Indian muntjac chromo somes, the C5 probe, which is derived from the centromeric satellite s equences of the Chinese muntjac, maps to the putative fusion points de termined by comparative chromosome painting and presumably represents the remnants of ancestral centromeric sequences.