Buccal cell genomic DNA was collected from Patient 1 (A), Patient 2 (B and C, two independently collected samples) and Patient 1’s mother (D). Patient 1 shows a heterozygous c.34G>A change, causing a G12S mutation, while Patient 2 carries low levels of the mutated allele. Father (B) and child (A) are heterozygous C/T at the −10 SNP, while the mother (D) is homozygous C and carries a wild type c.34G base.