Fig. 13. Denaturing gradient gel electrophoresis of polymerase chain reaction products containing exon 1 of the peripherin gene from members of a family with butterfly macular dystrophy. This method may be used to screen single patients or entire families with disorders for which there is a candidate gene. Each gel lane contains a sample from the person whose pedigree symbol is directly above the lane. Clinically affected persons are indicated by closed symbols, clinically unaffected by open symbols. Spouses are indicated by unnumbered symbols, which are connected to an affected patient's symbol by a horizontal line. Affected persons have multiple bands on the gel (representing homoduplexes and heteroduplexes caused by the presence of a mutation), whereas normal persons have only one band, corresponding to normal homoduplex molecules. (Nichols BE, Sheffield VC, Vandenburg K et al: Butterfly-shaped pigment dystrophy of the fovea caused by a point mutation in codon 167 of the RDS gene. Nat Genet 3:202, 1993)