RESUMO
This report introduces the second form of true albinism to be documented in sheep, which appears mild enough not to cause serious undesirable side effects yet apparently effective enough to have the potential for general usage in the sheep industry. Based on the matings conducted to date, the albinism is inherited like an autosomal recessive. Histochemical tests reveal a defective melanin synthesis involving a block to the conversion of tyrosine to dopa but not the subsequent reactions that lead to melanin. The enzyme tyrosinase is a product of the C locus and catalyzes the conversion of tyrosine to dopa and the following reaction (dopa to dopaquinone). Therefore, it is proposed that the albinism arises from a gene in the C locus that encodes a defective tyrosinase. The gene is provisionally named albino marrabel, the gene symbol is cmar, and the locus allele symbol is Ccmar.
