Studies of multiple allelomorphic series in the house-mouse

Summary

These experiments were chiefly addressed to the question whether the effects of changes at the same locus bear a purely quantitative relation to each other. The wild type and three mutant changes at the c locus have been examined in seven different compounds in combination with black (B) and seven in combination with brown (b). The effects of these changes on the dark granular melanins of the hair have been observed. In combination with black, the reduction in intensity of hair colour by graded steps from full colour (black) to white is accompanied by a parallel graded reduction in the quantity of melanin as measured by weight. The chief tangible factor in this reduction in quantity is the decrease in the size of the pigment granules. Each mutant gene in thec series thus exerts a characteristic effect on granule size. It is probable that the type of melanin molecule which is affected by these mutations is the same in all genotypes. As far as our data go, the changes brought about by mutations at this locus may be described as alterations in the quantity of melanin produced.