Heterozygous females are very similar to Atp7a^Mo/+ females in appearance but have normal viability. They have curly vibrissae, but the coat is not noticeably waved. Hemizygous males are almost devoid of pigment except in the eyes and ears. The vibrissae are strongly curled, and the coat is wavy. The abnormalities of hair structure have been described by Gr\"uneberg (J:5137). Males usually die when 2 weeks old, but a few have lived and been fertile. They have a behavioral abnormality consisting of a slight tremor, uncoordinated gait, and clasping of the hindfeet when held up by the tail (J:249, J:164). Females homozygous for Atp7a^Mo-br, and also heterozygous Atp7a^Mo-br/Atp7a^Mo and Atp7a^Mo-br/Atp7a^Mo-to females are identical in phenotype to hemizygous Atp7a^Mo-br males and die at the same age (J:164, J:12963). Histological examination of the brain of brindled males shows widespread neuronal degeneration in the cerebral cortex and thalamic nuclei and scattered degeneration in the cerebellum (J:6113). Heterozygous females have been shown to have neurochemical abnormalities as well (J:2026). In contrast to mice bearing other Atp7a alleles, brindled mice have no aortic lesions (J:12963) and no defect in crosslinking of collagen and elastin. Brindled males do, however, have a 30 to 40% reduction in lysyl oxidase activity in skin (J:5777). They have reduced synthesis of noradrenalin by dopamine--hydroxylase in the brain and peripheral nervous system (J:5323), and decreased activity of cytochrome C oxidase and superoxide dismutase (J:5830). These enzymes are all copper-dependent or copper-containing, and their reduced activity may be due to defective copper transport in cells of all affected tissues (J:5956, J:617, J:5747, J:12937). Brindled males have defective placental transport and defective intestinal absorption of copper. Copper concentration is high in gut mucosa, kidney, and testis and low in liver, brain, plasma, and most other organs (J:6204, J:6206). Concentration of the copper-binding protein metallothionein in various tissues is correlated with the concentration of copper (J:7370); however, hepatic metallothionein is inducible at normal levels in mutant neonates (J:24041). Parenteral injection of copper at 7 to 10 days of age has a striking therapeutic effect; it prevents tremor and early death, allows normal pigmentation, improves growth, produces normal concentrations of copper in organs previously deficient (except liver), produces normal activity of some copper-dependent enzymes (J:6205, J:7521), and prevents neuronal degeneration (J:6544). In heterozygotes with tabby (Eda), Atp7a^Mo-br resembles Atp7a^Mo-blo, and thus appears to act on coat color through an effect in hair follicles (J:5238).