A Comparative Study On Genetic Polymorphism In Mongolian Cattle And Japanese Black Cattle

The restriction fragment length polymorphism( RFLP) of mitochondrial DNA(mtDNA) of 13 Mongolian cattle breeds were studied using 12 restriction endonucleases recognizing 6 basepair, BamH I ,Bgl II ,EcoR I ,EcoR V ,Hind ni,Kpn I ,Pst I ,Pvu II ,Sac I ,Sal I ,Sca I and Xho I ,and compared with Japanese black cattle (Watanabe et al,1985), for investigation of the phylogenetic relationship between them. In Mongolian cattle, 5 of these(BamH I ,Bgl II ,Hind III,Pst I and Sac I )were found to be polymorphisms. Total 31 restriction sites and 17 restriction morphs were detected , which could be sorted into 3 haplotypes. Haplotype II and III (main haplotypes of Mongolian cattle) are distributed in mongolian cattle breeds with relatively high frequency ,i.e. 46.15%and 46.15%, respectively. The frequency of haplotype I is lower(7.69%).Haplotype II and III are shown the type of yellow cattle(Bos taurus), and Haplotype I is shown in that of zebu cattle(Bos indicus). In Japanese black cattle, only one of these restriction endonucleases, HindIII, was found to be polymorphisms. Total 34 restriction sites and 13 restriction morphs were detected, which could be sorted into 2 haplotypes (Haplotype IV and V ) . The frequency of haplotype V (main haplotype of Japanese black cattle)is higher(71.43%) and haplotypeIVis lower (28.57%) . The genetic distance between haplotypes and polymorphic degree( value) were alsocalculated according to the methods of Nei's. The results show that genetic distance between main haplotypes of Mongolian cattle and Japanese black cattle are 2.610% and 2.703% respectively. It implies that the relationship between Japanese black cattle and Mongolian cattle is more distant. According to that the rate of sequence divergence of mtDNA is estimated to be 2% per million years, Haplotype II and III of mongolian cattle' s mtDNA might be separate about 240 thousand years ago, which is earlier than the 10000-year history of cattle husbandry. Haplotype of yellow cattle (haplotype I )and zebu cattle(Haplotype II andIII) might be separate about 0.73-0.92 million years ago. Frequencies of haplotype I , II and III are different in each Mongolian cattle populations, maternal ancestors of haplotype II give more genetic contribution to Mongolian cattle breeds located in Wuzhumuqin region, but maternal ancestors of haplotype III give more genetic contribution to Mongolian cattle breeds located in Xilinhot region. They might be separate about 140 thousand years ago. The average genetic distances between haplotypes and the polymorphic degree of Mongolian cattle populations were 0.0126 and 0.219%, respectively. It is always considered quite low(0.15%-0.47%).