Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/1996
Publication Date: N/A
Citation: Interpretive Summary: Molecular genetics holds great promise for improving accuracy in selection of breeding stock. To realize this promise requires identifying variation in genes present at specific locations on chromosomes and associating that variation with differences in economically important traits. Four distinct sub-populations of Hereford cattle differing in expression of growth to one-year of age were characterized for genetic variation at eight chromosomal locations. Genetic variation existed at six of the eight locations examined in all sub-populations. However, differences between populations were not definitively associated with explanatory mechanisms. Associations of gene frequency with growth traits were then examined in the Miles City Line 1 population. Significant differences in gene frequency were found between populations indicating genetic divergence of them. Specific genes were identified that accounted for up to 16% of the total variation in genetic merit for growth traits in Line 1. These results are of particular importance to scientists attempting conclusive identification of genetic markers for growth traits of beef cattle.
Technical Abstract: Three populations of Hereford cattle differing in inbreeding levels and genetic potential for growth were genotyped for seven DNA polymorphisms. The populations were compared to determine differences in allele frequency and genetic variation, and existence of Hardy-Weinberg equilibrium was tested. Significant differences in allele frequency among the populations were found at six of the seven polymorphisms genotyped. Average genetic variation in the populations differed as expected when inbreeding levels were considered, and expectations of Hardy-Weinberg equilibrium were met for all but two polymorphisms. Effects of several polymorphisms on growth and maternal EPD were evaluated for one population (Miles City Line 1 Herefords) using regression analysis. Substitution of a B allele for an A allele of the kappa-casein polymorphism accounted for significant decreases in direct birth weight and maternal 180-d gain from birth to weaning EPD, explaining 15% and 8%, respectively, of EPD variability. Several other significant effects accounting for small portions of EPD variability were also detected.