TRANSMISSION OF MITOCHONDRIAL-DNA HETEROPLASMY IN NORMAL PEDIGREES

The presence of multiple mitochondrial genotypes (heteroplasmy) has be en studied in normal individuals. Six multigenerational normal familie s were screened for heteroplasmy by PCR of the mitochondrial control r egion and the cytochrome c oxidase intergenic regions. Two individuals from different families exhibited multiple length polymorphisms in a homopolymeric tract at positions 16184-16193 and a grandmother in a th ird family was heteroplasmic for both cytosine and thymidine at positi on 15945, Although the 15945 T variant comprised 28% of the grandmothe r's mitochondrial DNA, this sequence was not present in ally of her de scendants, Heteroplasmy was detected in 2.5% of the 96 mother-offsprin g pairs, consistent with the possibility that it may not be rare.