ARS | Publication request: EVALUATION OF PATERNAL POLAR OVERDOMINANCE BASED ON ALL POSSIBLE MATINGS AMONG CALLIPYGE (CLPG) GENOTYPES

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1999
Publication Date: N/A

Technical Abstract: Paternal polar overdominance uniquely associates the CN genotype (C represents the mutant CLPG allele and N the wild type allele, with the paternal allele given first) with the callipyge muscle-hypertrophy pheno- type and CC, NC, and NN genotypes with the normal phenotype of sheep. This form of parental imprinting was originally proposed based on data recorded on progeny of five CLPG mating types (CCxNN, CNxCN, CNxNN, NCxNN, and NNxCN, with the sire genotype given first). We used a complete 4x4 mating design of CLPG genotypes to evaluate the paternal polar over-dominance model of gene action. Data were recorded on 287 F3 lambs produced by 8 F2 sires and 152 F2 dams of Dorset-Romanov origin. Genotypic data from eight markers flanking the previously determined CLPG interval were used to calculate CLPG genotypic probabilities in the four-generation pedigree. Lambs were slaughtered and leg muscling scores assigned to carcasses. Lambs swith scores less than 13 (13=low prime) were considered of normal pheno- type, whereas lambs with scores greater than 13 were classified as calli- pyge phenotype. Phenotypic classification was regressed on CN probability to test the hypothesis of paternal polar overdominance. Residual analysis identified 15 observations associated with 96% of the error sum-of-squares. CN probabilities were intermediate for 7 lambs due to recombinations between flanking markers or lack of flanking marker information. Leg scores of 12 were assigned to 7 lambs with CN probabilities greater than .997 and the remaining lamb received a leg score of 14, but had a CN probability of less than .001; these results suggested errors in phenotypic classifica- tion. The experiment failed to provide conclusive evidence against paternal polar overdominance as the model of gene action at the CLPG locus.