The accuracy of an estimated breeding value depends on 3 factors: the heritability (h2) of the trait, the number of animals (N) in the reference population, and a parameter called q. The q is a population and trait specific parameter that combines information on the length of the genome with the level of inbreeding for that trait in that population. It is an estimate of the number of independent chromosomal segments. The SNP that are closely together on a chromosome will inherit together without recombination between them. The further apart two SNP are, the more likely it is that there will be a recombination event between them. The higher the inbreeding level, the higher the level of homozygosity on the genome, and thus the less recombination will result in a change in combination of SNP alleles between two SNP. An independent segment is a measure for the likelihood that there will be recombination resulting in different allele combinations. The longer the genome, the more independent chromosomal segments there will be. This is a complicated story. For now it is sufficient to remember that q is specific for a population and may have different values for different traits. Details go beyond the scope of this course. In a formula the accuracy of genomic selection can be expressed as:
Thus:
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The accuracy of genomic selection depends on the heritability, the number of animals in the reference population, and a population parameter q that reflects the relation between the size of the genome and level of inbreeding |