Fig. 2. Critical steps in the tanning pathway. (A) Metabolites of dopamine are required for tanning. Tyrosine hydroxylase (encoded by ple) converts tyrosine into dopa and dopa decarboxylase (encoded by Ddc) catalyses the conversion of dopa to dopamine. (B) Alternative splicing of ple and Ddc. Both ple and Ddc are alternatively spliced to produce neural-specific (shown above exon boxes) and epidermal-specific (shown below exon boxes) transcripts. The coding sequence is shaded in grey.