Association of dominant marker traits and metric traits in chickens.

This study was initiated to determine whether an allelic substitution of a dominant marker gene would identify a region close to a locus affecting expression in a metric trait. The rationale for the experiment was to utilize disequilibrium between a multiple recessive randombred Rhode Island Red (RRc) stock previously selected for quantitative trait performance and an unimproved dominant marker stock (MDM). The reporter genes in the MDM were: barring (B), silver (S), creeper (Cp), rose comb (R), double uropygial gland (U), crest (Cr), dominant white (I), frizzle (F), duplex comb (D), multiple spurs (M), polydactyly (Po), blue egg (O), pea comb (P), naked neck (Na), extended black (E), white skin (W+), muffs and beard (Mb), and feathered shanks (Fsh). Appropriate reciprocal crosses of MDM with RRc and F1 to RRc produced segregating full sibs that were evaluated for association with reporter traits. Carriers of Cr, I, and F were significantly later in sexual maturity than their recessive full sibs. The pleiotropic effects of F are believed to account for the later maturity. None of the marker traits had a significant association with egg numbers or egg weight. Birds expressing E were distinctly heavier at 8 and 32 wk. There is no obvious explanation for the significant larger size for the E phenotype. The CR-I-F phenotypes were significantly smaller at 32 wk than noncarrier full sibs.