The expression of the Tabby and crinkled genes in different genetic backgrounds in the mouse.

WO mutants in the mouse, Tabby and crinkled, produce identical phenotypes when homozygous. The Ta/Ta or cr/cr mouse has a long, narrow face, a very smooth looking coat with bare patches behind the ears, no hair on the tail and a markedly reduced number of secondary vibrissae (FALCONER, FRASER and KING 1952). The coat of the mouse normally consists of four types of hair: guard hairs, awls, auchenes and zigzags (DRY 1962). Closer examination of the hair of Ta/Ta or cr/cr mice reveals that the coat consists entirely of one type of hair which resembles an awl in length and shape but lacks the orderly arrangement of pigment granules found in normal awls (Figure 1) . The mutants differ in that