Study On MtDNA Polymorphism And Relationship Between National Cattle Strains From Northern China

Mitochondron is unique extranuclear heredity factor in mammal and also the center of energy metabolism, which can biosynthesis fatty acid and some protein.Mitochondrial D-loop region is the unique noncoding region, which have maximal variation in mitochondrial genome, including sequence composition and length. Cytochrome B (CytB) is in charge of transferring electron on mitochondrial respiratory chain. It is also the unique coding protein in mitochondrial genome. In field of phylogenic evolution research, it is always an available molecular labeling. More and more mammalian phylogenesis was analyzed with CytB gene polymorphism recently.Mitochondrial DNA polymorphisms contributed to nucleotide and number variation that existed in mitochondrial DNA hypervariable region. There are five types of mutation, including transition, transversion, insertion, deletion and the coexistance of transition and transvertion.The kimura 2-parameter distances and base substitution, composition, variation were analyzed with MEGA software, the percentage differences among them were calculated with DNAstar software, and the polymorphic sites were analyzed with DNAsp software. The phylogenic trees constructed by three methods (UPGMA-tree,NJ-tree,ME-tree) which supported almost the same topology. The topology structures of different phylogenic trees were similar and discrepancies are not significant. It indicated that phylogenic trees wereaccurate.The polymorphism of D-loop complete sequence and CytB gene partial sequence with northern cattle strains including Luxi yellow, YanBian yellow, CaoYuan red and alien Japan black cattle were studied in this research. The relationship of four populations was analyzed with bioinformation methods.The results of mtDNA D-loop(CytB) polymorphism analysis showed that there were 7(2) haplotypes in 8 Luxi Yellow, the average haplotype diversity was 0.964±0.006 (0.536±0.123); 9(3) haplotypes in 11 Japan Black, the average haplotype diversity was 0.964±0.003(0.473±0.162); 9(3) haplotypes in 10 YanBian yellow, the average haplotype diversity was 0.978±0.003 (0.182±0.144); 11(5) haplotypes in 11 CaoYuan red, the average haplotype diversity was 1.000±0.005(0.644±0.152).D-loop Kimura 2-parameter distance between breeds were 0.0162, 0.0190, 0.0196, 0.0308, 0.0333, and 0.0354 respectively. By pairwise comparison, the closest distance was 0.0162 between Japan Black and YanBian yellow; the farest distance was 0.0354 between Luxi yellow and YanBian yellow. The phylogenic analysis revealed that the Luxi yellow cattle is the farest relation to the other breeds, the Japan black is more closely related to the YanBian yellow than to that of the other breeds.Cyt B Kimura 2-parameter distance between breeds is 0.0025, 0.0035, 0.0040, 0.0063, 0.0077, and 0.0078 respectively. By pairwise comparison,the Luxi yellow is also the most farthest relation to the other breeds. Japan black cattle 489,463 is special compared with the other cattle intraspecies. It suggests that maybe they are hybrid individuals.