Evaluation of frequency of the favorable allele of major gene under overlapping and discrete generation: A study based on simulation

Litter size (LS) is one of the important economic traits in sheep . This trait is influenced by some genes with a large effect. The purpose of this simulation study was to evaluate the fixation selection designs for favorable major gene allele under scenarios of overlapping and discrete generations. In this regard, a trait with heritability of 0.1, and a genome with 26 chromosomes and a major gene was simulated in sheep population. Animals breeding value was predicted using Bayesian threshold model. Selection of animals was based on estimated breeding value (EBV), phenotype (PHEN) and random (RND). After ten generations, genetic gain in selection based on EBV, PHEN and RND under scenario of discrete generation were 8, 23 and 26 percent higher than those in scenario of overlapping generation, respectively. The accuracy of prediction in scenario of discrete generation was higher than scenario of overlapping generation. Means of inbreeding coefficient under scenario of overlapping generation and selection for EBV, PHEN and RND were 0.317, 0.029 and 0.027, respectively, and for scenario of discrete generation were 0.327, 0.058 and 0.056, respectively. In generation ten, the favorable allele of the major gene, in scenario of discrete generation selection based on EBV, PHEN and RND was 1, 46 and 38 percent higher than those in the scenario of overlapping generation, respectively. The results indicated that the scenario of discrete generation selection based on EBV leads to more fixation the favorable allele of the major gene and of genetic gain.