Chromosome evolution of the Malayan gaur (Bos gaurus hubbacki)

A GTG-banding comparison between the chromosomes of gaur (Bos gaurus hubbacki, BGA, 2n = 56) and those of domestic cattle (Bos taurus, BTA, 2n = 60) was performed to establish chromosome homoeologies or differences between the two species. The two biarmed chromosomes of gaur (BGA1 and BGA2) were originated by centric fusion translocations between homoeologous cattle chromosomes 1/29 (BGA1) and 2/28 (BGA2). High resolution GTG-banding comparison between BGA1 and BTA1/BTA29 revealed that BGA1q differentiated from BTA1 by a paracentric inversion of a large and proximal chromosome region (BTA1q13-q32). To our knowledge, this is the first case of a bovid biarmed chromosome originated by centric fusion and paracentric inversion during karyotype evolution. The CBG-banding pattern showed clear C-bands in all autosomes, although the two biarmed pairs showed smaller C-bands, especially in BGA2. The results were discussed on the basis of previous results obtained in other bovid species, including the carriers of rob(1; 29) of cattle, the most known and widely spread chromosome abnormality in Bos taurus.