AGOUTI LOCUS: HOMOLOGY OF ITS METHOD OF OPERATION IN RATS AND MICE.

The action of genes at the agouti locus in rats is similar to that of genes at the same locus in mice-the color phenotype of hairs is determined by the operation of agouti-locus alleles in the follicle, rather than in the melanocytes. Hairs produced by mouse skin growing on partially tolerant infant rat hosts show that rat melanocytes also respond to the agouti-locus genotype of mouse follicles. This constitutes the first example in vivo of the behavior of a cell of one species being completely determined by the genotype of an alien host species.