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GPOi, _ a it is not expected to change the average phenotypic value. However, variation in phenotype about the average will be caused by both VG and VE.

Examine the expression for the mean genotypic values for each marker genotype in Table 9.5. If there is free recombination between the QTL and the marker locus, r = 0.5 and the marker locus segregates independently of the QTL that influences phenotype. With free recombination between the M and Q loci, the marker class genotypic means should not differ because the marker genotype is not associated with the QTL genotype. You can see that this is true by solving each marker class mean for r = 0.5 and finding that the expected mean for all marker genotypes is 0.5d. Therefore, when M is not associated by linkage with a QTL locus there should be no difference between the marker class means GM M and Gm m . If, on the other hand, the average phenotypic values of those individuals with different marker genotypes are different, then this is evidence that there is a QTL linked to the marker. In other words, a difference between GM M and GM M is evidence that the marker locus is located inside a linkage block that also contains a QTL.

Given a difference between G

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