Detecting Rare Triple Heteroplasmic Substitutions in the Mitochondrial DNA Control Region: A Potential Concern for Forensic DNA Studies

(Pages: 103-106)
Saeid Morovvati, M.D.Ph.D., 1,*Ziba Morovvati, M.Sc., 1Reza Ranjbar, Ph.D., 2
* Corresponding Address:P.O. Box: 19945-581 Research Center for Human Genetics Baqiyatallah University of Medical SciencesTehran Iran Email:
Any use, distribution, reproduction or abstract of this publication in any medium, with the exception of commercial purposes, is permitted provided the original work is properly cited This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Morovvati Saeid, Morovvati Ziba, Ranjbar Reza. Detecting Rare Triple Heteroplasmic Substitutions in the Mitochondrial DNA Control Region: A Potential Concern for Forensic DNA Studies. Cell J. 2011; 13(2): 103-106.



Mitochondrial DNA (mtDNA) is a useful tool for population studies, identification of humans and forensic DNA studies. The existence of several hundreds copies of mtDNA per cell permit its extraction from minute or degraded samples. In addition, the level of polymorphism in the hypervariable (HV) region is high enough to permit its use in human identity testing. However, the presence of several heteroplasmy might lead to ambiguous results.

Materials and Methods:

This study was an experiental study. This study evaluated heteroplasmy in the HV region of mtDNA in blood samples of 30 Iranians who belonged to ten unrelated families from three sequential generations (grandmother, mother and daughter).


There were no heteroplasmic substitutions in the HV1 region, but analysis of HV2 showed heteroplasmic substitutions in two out ten families. In the first family the grandmother showed heteroplasmy (T/C) in nucleotide positions 146 and 151, however it was not detected in the mother and daughter. In second family, a triple heteroplasmy (T/C) was detected in the daughter in nucleotide positions 146, 151 and 295, but these heteroplasmic substitutions were not obvious in the grandmother and mother.


Heteroplasmy in mtDNA is not a rare phenomenon and probably exists in everyone, but a triple heteroplasmy in one family member is a novel finding. Our results demonstrate that one or two sequence differences between samples in mtDNA do not warrant exclusion. In our study, the average nucleotide difference between unrelated persons in the HV2 region was 2.8 nucleotides, whereas there was a triple heteroplasmy in one person which was not obvious in her family.