Plant & Animal Genome IX Conference Plant & Animal Genome IX Conference
Workshop: Coat Color
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Plumage color is a subject of study for mendelian genetics, and has been used by breeders to differentiate chicken breeds or varieties, and to practice auto-sexing at hatch. Pigment biochemistry and melanocyte morphology were studied in the 70s by Brumbaugh et al. Briefly, a phenotypic classification recognizes at least 15 major loci controlling various aspects of plumage color (white, variation of the black or red pigment). Pigment patterns are also observed on the feather, determined by single gene effects or by gene interactions. Phenotypic similarities have suggested some homology with mammalian mutations, the best example being the C locus and its albino allele characterized by an inactive tyrosinase. Molecular cloning of coat color mutants in the mouse provides now an array of candidate genes for an accurate identification of plumage color mutations. Two genes have been studied in detail, melanocortin-1-receptor, as a candidate for the E locus, and tyrosinase for the C locus. A small deletion in the TYR gene has been identified as the causal mutation of the albino allele by Tobita-Teramoto et al., and another allele, the recessive white with pigmented eyes, has been linked to a RFLP of the TYR gene in our laboratory. Regarding MC1R, we have investigated its polymorphism by direct sequencing in 18 chicken breeds differing at the E locus, and found 10 polymorphic sites in the coding region. Three sites appeared characteristic of a phenotype but it is clear that molecular typing will contribute to revisit the nomenclature of alleles at the E locus.