Heterozygous females carrying the brindled allele (Atp7a^Mo-br) are very similar to mottled heterozygous females (Atp7a^Mo/+) 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. Males usually die by two weeks of age, 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. 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. Heterozygous females have been shown to have neurochemical abnormalities as well. In contrast to mice bearing other Atp7a alleles, brindled mice have no aortic lesions and no defect in crosslinking of collagen and elastin. Brindled males have defective placental transport and defective intestinal absorption of copper. Parenteral injection of copper at 7 to 10 days of age prevents tremor and early death, allows normal pigmentation, improves growth, produces normal concentrations of copper in organs previously deficient (except liver), producesnormal activity of some copper-dependent enzymes, and prevents neuronal degeneration.