Inter-and Intra-individual Polymorphism in MtDNA Control Region: a Preliminary Report on MtDNA Haplotypes, Inheritance and Segregation of Heteroplasmy in 10 Maternal Pedigrees

The high copy number and maternal inheritance property of human mitochondrial DNA (mtDNA) has made it a favorable tool for forensic investigations. Especially, the mtDNA control region contains highly variable regions that are exploited by the forensic scientists for identification purposes. In the present study, hypervariable regions I, II and III (HVRI, HVRII and HVRIII) were determined by direct sequencing from samples derived from 10 maternal lineages, spanning three generations. Interfamily comparison led to the identification of 10 different haplotypes belonging to haplogroup W, M, U and R. We have also determined the presence of sequence and length heteroplasmy - its inheritance and segregation amongst the maternally related members of the family, in blood and buccal cell DNA. One instance of point heteroplasmy in family 2, HV1 homo-polymeric tract heteroplasmy in 4 families and HV2 poly- C tract heteroplasmy in all the 10 families with varying degree was observed. A typical pattern of segregation of length heteroplasmic pool was also observed in family 1. The existence of germline as well as somatic heteroplasmy greatly affects the interpretation of mtDNA data in forensic investigation. We have attempted to understand the segregation phenomenon of multiple mtDNA haplotypes at the germline as well as somatic level.