The effect of major gene parameters on the rate of changes in genetic variance of dairy cattle population
Abstract:
Intense selection for quantitative traits has recently led to the unexpected appearance of new genes with major effects. The information of such genes or their linked markers can increase the accuracy of selection. In this research a population of dairy cattle with overlapping generations in presence of a major gene was generated. This research was completed between years 1385 and 1386 in Varamin Azad University, using personal computers. Different modes of major gene inheritance (different initial frequency of favorable allele, different magnitude of additive effect and various degree of dominance) in addition to different values for polygenic heritability lead to various combinations. The changes of some variances (major gene, polygenic, total additive and phenotypic variance) were investigated in each combination. The speed of these changes was calculated by the regression coefficient of changes over a 20- years period selection.. The magnitude of major gene’s effect was shown as the level of its contribution to total additive variance. The relation between speed of changes and level of contribution was studied. Speed of changes in major genes variance, total additive variance and phenotypic variance was regressed significantly over the level of contribution. But this relation was not significant for the polygenic variance. As a conclusion, the existence of major genes with large effects in such populations leads to reduced rate of changes in variance and lack of diversity.
Language:
Persian
Published:
Iranian Journal of Dynamic Agriculture, Volume:4 Issue: 1, 2007
Page:
11
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