The sequences of the two hypervariable regions of the mitochondrial DNA control region (HV1 and HV2) from close maternal relatives (mother-child pairs) were compared to determine the frequency of mutations between two generations. A total of 68 blood samples were sequenced only in HVI and 86 were analysed for HV1 and HV2. The intergenerational comparison led to the identification of six heteroplasmic point mutations affecting the children only. In one case a heteroplasmy of the maternal sequence was resolved to homoplasmy in the corresponding sequence of the child.