Fig. 4

Polyacrylamide gel electrophoresis confirmed that the nucleotide substitution c.35G > T co-segregated with the disease phenotype in the family. The variant was observed in the proband and her affected mother, aunt, and grandmother, but not in her unaffected father, sister, grandfather or 100 unrelated Chinese controls. The PCR product was 159 bp in length and contained a Sac1 site. The mutant allele contains a Sac1 restriction site and can be digested into two fragments (135 bp, 24 bp) by Sac1, but the wild-type allele cannot be digested. Affected individuals show two bands (135 bp and an undigested band of 159 bp) on an 8% polyacrylamide gel. All the unaffected members show only a single undigested band of 159 bp