PpiI restriction pattern of the human intron 6 fragments amplified with primers INT-6s and NTR-4as (Table 1 ). Wild type (1), heterozygous blood donor (2), and maternal homozygous (3) with the double CACT insertion. A single undigested band of 892 bp is seen with the wild type. The heterozygous individual presents the wild-type 892-bp band and 2 lower bands of 622 and 242 bp from the digested mutated allele. The maternal sequence presents the homozygous mutated profile with the 2 digested bands of 622 and 242 bp. The Ppi I enzyme cuts twice before and after the digestion site, giving 2 large fragments of 622 and 242 bp and a small fragment of 32 bp (not shown).