CYP2D6 and melanoma: Only the CYP2D6 gene was greatly differentially expressed between the birds from the absent and severe HVP groups (p < 0.05), and CYP2D6 had a much high level in the server individuals, which was consistent with the studies in humans that CYP2D6 genotypes were associated with the hair color, Breslow thickness, and malignant melanoma (Strange et al., 1999).