c.2747C>G segregates CDA III in the American family. (A) Pedigree of the family with affected individuals shown in black symbols and healthy individuals shown as unfilled symbols. DNA was available only for cases marked with A1–A6. (B) Restriction length fragment polymorphism assay. Amplification of exon 21 of KIF23 was done as described in “Materials and Methods.” PCR products were digested using the HpyCH4IV endonuclease. c.2747C>G creates a restriction site; therefore, all mutation carriers show 3 bands—338, 175, and 163 bp (small fragments are poorly resolved on agarose gel)—whereas all unaffected individuals show only 1 band (338 bp).