The gene for a red hair colour (RHC) variant (p.Arg151Cys or p.R151C) of human melanocortin 1 receptor was placed downstream of the mouse tyrosinase enhancer/promoter. Bovine growth hormone poly(A) signal sequences were placed downstream of the human gene. The transgene construct was microinjected into zygotes derived from Mc1r knockout mice containing the Mc1re allele. (J:252840)