A “new” allele at the C pigment locus in the fowl

A genetically defined autosomal albino (a) stock of the domestic fowl was developed. By appropriate crosses it was found to be an allele of recessive white (C), but not pink eye (pk) or blue (Bl). Its allelism with recessive white necessitates a change in symbol since it was thought to be at a separate locus. Therefore the C locus in the fowl is multipleallelic. The most dominant allele is wild type, C+, which allows full pigmentation. The most recessive allele is autosomal albinism, which allows the least amount of pigment to develop. The symbol ca would appropriately designate this allele. The slightly more pigmented (faint yellow tinge) allele, which is incompletely dominant to Ca, is the recessive white mutation, c. Concomitant electron microscope studies of both retinal and feather melanocytes were made, which showed both mutant alleles are cytothemically tyrosinase negative, possess hypertrophied golgi systems, and contain numerous vesicles that appear to be incompletely formed, unpigmented granules. Retinal melanocytes possess a few pigmented granules, more in recessive white (C) cells than in albino (Ca) cells.