Human CYP2D6*2N allele, a variant form of the CYP2D6 wild-type allele, is approximately 4 kb in length and encodes cytochrome P450 2D6 protein. Amplification of the CYP2D6 gene (up to 12 copies) produces the CYP2D6*2N allele. The enzymatic activity of the protein encoded by this allele is not significantly different from the protein product of the wild-type allele. However, individuals who carry this allele exhibit an ultra-rapid metabolizer phenotype. [ ]