Transmission of mitochondrial DNA heteroplasmy in normal pedigrees

The presence of multiple mitochondrial genotypes (heteroplasmy) has been studied in normal individuals. Six multigenerational normal families were screened for heteroplasmy by PCR of the mitochondrial control region and the cytochrome c oxidase intergenic regions. Two individuals from different families exhibited multiple length polymorphisms in a homopolymeric tract at positions 16 184–16 193 and a grandmother in a third family was heteroplasmic for both cytosine and thymidine at position 15 945. Although the 15 945 T variant comprised 28% of the grandmother’s mitochondrial DNA, this sequence was not present in any of her descendants. Heteroplasmy was detected in 2.5% of the 96 mother-offspring pairs, consistent with the possibility that it may not be rare. Received: 18 August 1997 / Accepted: 10 November 1997