SSCP analysis of plasminogen gene exon 7 in patients no. 3 and 4 and her parents. Radiolabeled single-stranded PCR products of plasminogen exon 7 were electrophoresed in a nondenaturing 5% polyacrylamide gel as described in Materials and Methods. Lane 1, healthy control (C); lane 2, mother; lane 3, father; lane 4, patient no. 4 with ligneous conjunctivitis; lane 5, patient no. 3. dsDNA, double-stranded DNA. The double-stranded DNA of patients no. 3 and 4 (lanes 4 and 5) and of the mother (lane 2) shows two bands. The shorter band is the mutant allele with a 3-bp deletion (AAG) at position 767-769. Note that alleles a and d of the mother (lane 2) are slightly faster migrating when compared with bands a and d of a healthy control with the wild-type sequence (lane 1). This is due to two polymorphisms, a silent C → T base exchange at position 847 in plasminogen exon 7 (Cys₂₃₈) and a T → G base exchange at position −15 in plasminogen intron F.