Extent of heterogeneity in the poly-nucleotide stretches of MtDNA hypervariable regions in the Indian population

Mono-nucleotide and di-nucleotide repeats are observed to have high levels of allelic diversity and as such considered as mutational hot-spots. Such repeats are also found in the hyper-variable regions (HVR) of human mitochondrial DNA (mtDNA). A poly-cytosine (poly-C) stretch located within the HVR1, HVR2 and HVR3 regions exhibits high degree of polymorphism. Another highly polymorphic stretch of CA-repeat is located in HVR3. To assess the discrimination power of the alleles at these loci and their cumulative capability to provide interpersonal information, we have screened 200 Indians that belong to the Indo-European ethnicity. We have determined the distribution of different length variants in the given population and the frequency of the variantin these individuals. We identified 37 mtDNA haplotypes when all the length variants within these four regions were considered. The frequency of length heteroplasmy was very high in HVR2 (55.5%) as compared to HVR1 (7%) and HVR3 (1%). The increased knowledge concerning mtDNA length variations and heteroplasmy is believed to offer an applicable method of determining genetic identity due to increased mtDNA haplotype diversity.