Abstract:

【Objective】The objective of this study was to find the proper model of combined loci in analysis of genetic co-adaptability, and add the data of genetic co-adaptability theory on evolution mechanism difference of genetic co-adaptability among breeds or between closely related species-goat.【Method】Tan sheep, small-tailed Han sheep, Hu sheep, Tong sheep and Wadi sheep were regarded as the research objects and their closely related species-goat was served as the reference object, and 9 structural loci with different polymorphism were selected. 【Result】 The dominant-dominant model was not proper to be used in genetic co-adaptability analysis. The co-dominant-dominant model the co-dominant-co-dominant model could be used in genetic co-adaptability analysis. The principles of classic neutral gene genetic disequilibrium could explain most genetic disequilibrium between loci, but the principles could not fit for Tf locus with too many rare alleles, because it could not provide a rational explanation or the explanation was inconsistent. The differences in the coefficients of genetic co-adaptability, genetic disequilibrium and link disequilibrium between sheep and goat (among species) and breeds (within groups) decided by different loci combinations. 【Conclusion】 Genetic co-adaptability do not exist in the loci combination of dominant-dominant, but it may exist in the loci combination of co-dominant-dominant and co-dominant-co-dominant. Due to different origins, there is a large difference in genetic co-adaptability between sheep and goat, while the different breeds of sheep species with the same origin have a consistent tendency in genetic co-adaptability. This is the first time, that the regression equations of coefficients of genetic co-adaptability and genetic disequilibrium in different models were obtained, which will be helpful for research on function mechanism and calculation of genetic co-adaptability.

Key words: structural loci, genetic co-adaptability, sheep breeds, closed related