Detection of more than one base mismatch in PCR products for exon 30 of the COL1A1 gene. The PCR products of 236 bp each were obtained from seven unrelated individuals. For clarity, the mismatches are defined here as A (C−5IVS29A), B (T39IVS30C), C (A−41IVS29G), and D (G−43IVS29C). Lane 1, mismatches A and B. Lane 2, mismatches A, B, and C. Lane 3, mismatches C and D. Lane 4, mismatch B. Lane 5, mismatches B and C. Lane 6, mismatch C. Lane 7, control sample.