Direct detection of plasminogen mutation in family 2 by amplification mutagenesis. A part of plasminogen exon 15 containing the stop codon mutation (G → A) at position 1924) was amplified by PCR as described in Materials and Methods. The reverse primer has a single sequence mismatch that results in the introduction of an artificial Hinf I restriction site into the mutant exon 15 allele only. Amplified PCR products were digested with Hinf I and electrophoresed in a 2.5% agarose gel and visualized by ethidium bromide staining. The mutant Hinf I-digested PCR fragment has a size of 107 bp, the wild-type (uncut) PCR fragment has a size of 129 bp. −, No Hinf I added to PCR product; +, Hinf I added to PCR product. Lane M, 100-bp ladder; lane 1, patient 2; lane 2, mother of patient 2; lane 3, father of patient 2; lane 4, healthy sister of patient 2; lane 5, healthy control. The (shorter) mutant Hinf I-digested allele is found in patient 1 (lane 1+) and the parents (lanes 2+ and 3+, heterozygotes), but not in the sister (lane 4+) and the healthy control (lane 5+).