Mutations in the gene for the pigment-producing enzyme tyrosinase are 
responsible for type IA (tyrosinase-negative) oculocutaneous albinism (OCA). 
Most reported mutations have been single base substitutions. We now report three 
different frameshift mutations in three unrelated individuals with type IA OCA. 
The first individual has a single base deletion within a series of five 
guanidines, resulting in a premature stop codon in exon I on one allele and a 
missense mutation at codon 382 in exon III on the homologous allele. The second 
individual is a genetic compound of two separate frameshift mutations, including 
both the same exon I single base deletion found in the first individual and a 
deletion of a thymidine-guanidine pair, within the sequence GTGTG, forming a 
termination codon (TAG) in exon I on the homologous allele. The third individual 
has a single base insertion in exon I on one allele and a missense mutation at 
codon 373 in exon III on the homologous allele. The two missense mutations occur 
within the copper Bbinding region and may interfere with either copper binding 
to the enzyme or oxygen binding to the copper. These five different mutations 
disrupt tyrosinase function and are associated with a total lack of melanin 
biosynthesis.