| The genetic diversity of livestock lays the foundation for its sustainable, development, and only the well-conserved genetic resources will guarantee its selection and breeding. The assessment of genetic resources is a perquisite for conserving the genetic diversity. China is one of the countries who have the most abundant resources of cattle breeds, but yet there is no standardized molecular assessment system so far. In such a situation, the genetic diversity has been assessed on a molecular level through the microsatellite and mitochondrial DNA analysis.The microsatellite markers distributed in the nuclear genome represent the genetic information of organisms. The 26 markers used in this study were recommended by the FAO to identify polymorphism of cattle breeds. 394 individuals from 14 populations had been detected, including four Chinese indigenous cattle breeds, Yanbian cattle (64), Mongolian cattle (19) , Qinchuan cattle (22) and Luxi cattle (20) ; three developed breeds, Simmental (31) , Chinese Holstein (63) and Grassland Red Cattle (27); two European beef cattle breeds, Limousine (16) and Charolais etc. European beef cattle; four crossbreeds, crossbred of Charolais and Yanbian cattle (13) , crossbred of Limousine and Yanbian cattle (13), crossbred of Limousine and Grassland red cattle (28) and crossbred of Grassland red cattle and Danish Red(20); as well as a yak breed, Tianzhu White Yak.By using semi-automated fluorescence PCR, 330 alleles are genotyped from 26 microsatellite markers. The PIC of every marker ranges from 0.1247 to 0.8807 in all populations, yet all differs. Taking all the populations into consideration, the PIC of every microsatellite marker ranges form 0. 5367 to 0. 8861, providing a fruitful information that the average PIC is higher than 0.5. For all categories, the observed heterozygosty of every locus ranges from 0.2 to 0.9545, while the expected heterozygosty ranges from 0.2-0.9545.According to the results of the clustering analysis, Yanbian cattle and Mongolian cattle have a closer relationship in evolution, and so do Qinchuan cattle and Luxi cattle. In crossbreeds, LY and XY have a closer relationship with Limousine and European beef cattlerespectively. Holstein and the European beef cattle breeds selected in this study belong to the Bos Taurus as we know. Therefore, the clustering analysis further verifies the acknowledged genetic relationship that all studied cattle breeds belong to Bos Taurus except yak, of which Qinchuan cattle and Luxi cattle may have some gene flow from Bos indicus.The mitochondria are the only organelles which carries the extranuclear genetic materials in advanced animals. The highly-mutated D-loop zone and the sole complete gene CYTB in mitochondria! DNA are analysed for genetic variation. For individuals from 10 cattle breeds (Yanbian cattle, Mongol ian cattle, Qinchuan catt le, Luxi cattle Simmental, Chinese Holstein, grassland red cattle. Limousine, German Yellow cattle and Tianzhu White Yak), the"D-loop and CYTB gene of two randomly sampled individuals are amplified by PCR and sequenced.The analysis of a 910 bp long fragment from D-loop shows that two long deletions fragment occurs in yak, of which one is 10 bp and the other is 7 bp. Of all the 20 sequences from 10 breeds, there are 18 haploids, 164 point mutations, and 346 base pairs detected, of which 235 are transitions, 55 are transvertions, and the other 56 are insertions and deletions. Given the outcomes of the clustering analysis, it is found that all Yellow cattle except Luxi descended from two Bos Taurus cattle. Luxi descended from two matrilino: one is Bos Taurus, the other is Bos indicus. And yak and Yellow cattle derived from different matriline.By analysing the 1140 bp DNA sequence of CYTB gene, 10 haploids are genotyped of 20 sequences from 10 breeds, and haploids occur less frequently in Yellow cattle. Among 98 mutations, there is no insertion or deletion, and Yellow cattle and Yak have the same codon bias except the isoleucine codon. While translated to Amino acids sequence... |
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