On page 43, Yoon and colleagues use a chimeric oligonucleotide to restore pigmentation in hairs of albino mice. A point mutation in the gene for tyrosinase, a key enzyme in melanin biosynthesis, leads to loss of pigmentation in mice. The workers designed a chimeric oligonucleotide that would correct the point mutation, and applied it to mice topically or by intradermal injection. After treatment they observed that black pigmentation was restored in a small number of hairs. They confirmed that the point mutation was corrected by DNA sequence analysis, and that tyrosinase activity was restored by enzymatic assays (see also p. 20).