Polyacrylamide gel electrophoresis of the amplified 345-bp fragment of factor II gene after HindIII digestion; the mutant factor II gene has a restriction site for HindIII leading to the production of two 322- and 23-bp fragments (the latter not detectable here). The wild-type factor II gene is characterized by the presence of the only 345-bp fragment (lane 2). The mutant factor II gene heterozygous genotype (lane 1) is characterized by two fragments of 345 bp (wild-type allele) and 322 bp (mutant allele); the homozygous genotype shows only a 322-bp fragment (lane 3).