Mutation analysis and prenatal gene diagnosis for the mutated tyrosinase (TYR) gene in two families with oculocutaneous albinism type I (OCA1).To define the fetus genotypes and gene mutation sites, the PCR and sequencing techniques were applied to amplify and analyze the regions of exon, exon-intron and promoter of TYR gene in probands and their parents of 2 families.The patient or proband of family 1 showed as a compound heterozygote with mutants R278X and 929insC