Direct detection of missense mutation Arg₅₁₃→ His in plasminogen exon 13 by RFLP analysis. Amplified PCR products of plasminogen exon 13 were digested with Mae III, electrophoresed in a 2% agarose gel, and visualized by ethidium bromide staining. The (uncut) mutant type PCR fragment has a size of 184 bp; the wild-type Mae III-digested PCR fragment has a size of 139 bp. −, no Mae III added to PCR product; +,Mae III added to PCR product. Lane M, 100-bp ladder; lane 1, father of patient no. 1; lane 2, mother of patient no. 1; lane 3, brother of patient no. 1; lane 4, patient no. 1; lanes 5 through 8, healthy controls. The larger (mutant type) allele is found afterMae III-digestion in patient no. 1 and his mother (lanes 2+ and 4+, heterozygous), but not in the father and the brother of patient no. 1 (lanes 1+ and 3+) and not in 4 healthy controls (lanes 5+, 6+, 7+, and 8+).