Figure 3. Screening for the 417C>T (R124C) mutation using polymerase chain reaction-restriction fragment length polymorphism. Exon 4 was amplified from individuals III-1, IV-10, IV-13, V-15, V-17, V-19, and V21 of Family One, I-1, I-2, and II-1 of Family Two, and I-1 of Family Three and the PCR product were digested with PstI restriction enzyme. After digestion, the products were analyzed using 3.5% agarose gel electrophoresis. Allele 417C generates two DNA fragments of 124 and 97 base pairs, and allele 417T generates three DNA fragments of 124, 76, and 21 base pairs. The 21 base pair fragment cannot be observed in this kind of agarose gel electrophoresis. Patients III-1, IV-10, IV13, V17, and V-19 of Family One and II-1 of Family Two are heterozygous for the 417C>T mutation, and individuals V-15 and V21 of Family One, I-1 and I-2 of Family Two, and I-1 of Family Three do not carry the mutation.