ABSTRACT
The phenotype of si/si mice is highly dependent upon the background genotype (see genetics). Although homozygous brown silver (b/b, si/si) mice show less silvering than black silvers (B/B, si/si), paradoxically, the effect of silver is greatly intensified in mice carrying the brown allele in the heterozygous state (B/b, si/si). Recently, the gene encoding PMEL 17 (gene symbol: D10H12S53E), a melanocyte-specific protein, has been located to Chromosome 10 in the mouse and to the homologous Chromosome 12 in man. As with man, domestic animals with heavily pigmented hair may develop mild graying with age. Recessive spotting (rs, Chromosome 5) maps very close to silver and also has the phenotype of slow melanocyte proliferation. In addition to its potential utility in studying the process of graying, the silver mutation provides a useful model for investigating the mechanisms involved in radiation sensitivity of melanocytes.
