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Abstract

The melanocortin 1-receptor (MC1-R) gene plays a key role in the expression of fur and feather color in mammals and birds by regulating the distribution of two melanin pigments: eumelanin (black/brown) and pheomelanin (red/yellow). MC1-R corresponds to the classical Extension (E) locus in mice, pigs, dogs, horses, and chickens. Three E locus alleles, the wild-type (e + ), brown (E), and redhead (e rh) have been identified in Japanese quail (Coturnix japonica). To determine if the quail E locus phenotypes were due to variation in the MC1-R gene, the coding region of the MC1-R gene was PCR amplified and DNA sequenced using genomic DNA isolated from individuals exhibiting the phenotypes of the three quail alleles. The DNA sequence comparison revealed two missense mutations that differentiated the brown from the wild-type and redhead quail. A single-base substitution resulted in a Val58Ile change, and another single-base substitution produced a Glu92Lys change in the brown quail. The redhead quail sequence carried a seven-base deletion extending from nucleotide position 682 to 688, resulting in a reading frame shift and premature termination of the MC1-R gene after amino acid position 231. The Glu92Lys change in the brown allele created a Msc I restriction fragment length polymorphism (RFLP). A PCR-Msc I RFLP test was developed and a direct correspondence between phenotype and genotype was found by testing the DNA of a population segregating for the brown and wild-type alleles. The DNA sequence and segregation data indicate that the quail E locus is homologous to the E locus identified in other birds and mammals.

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