The effectiveness of sequence variants of MTCOI and MTCYB besides entire D-loop for haplotyping in eight population groups living in Taiwan

Objectives: Analysis of human mitochondrial DNA (mtDNA) polymorphisms of hypervariable regions has become an important tool in forensic casework. This study evaluates the usefulness of the coding region polymorphisms in addition to hypervariable regions of different populations to increase the value of mtDNA polymorphic data in forensic genetics. Methods: The sequence polymorphisms and haplotype frequencies of MTCOI, MTCYB, and the entire D-Loop of mtDNA, including hypervariable regions 1,2, and 3 of 432 individuals of eight population groups living in Taiwan, including Taiwanese Han, indigenous Taiwanese of Taiwan Island, Tao of Orchid Island, mainland Chinese, Filipinos, Thais, Vietnamese, and Caucasians were analyzed. Results: Sequence positions with high heterogeneity were observed in D-Loop, MTCOI as well as MTCYB. Among the 432 subjects, 317 different haplotypes were observed for a combination of MTCOI, MTCYB, and entire D-Loop sequences, and 268 haplotypes were noted only once. The forensic parameters were calculated for different combinations of mtDNA regions. In most of these populations, sequence variants of MTCOI and MTCYB could further discriminate the haplotypes, besides the polymorphisms of hypervariable regions 1 and 2. The effectiveness of sequence variants of MTCOI and MTCYB for further haplotype differentiation varies in different population groups. Conclusions: In addition to the polymorphisms of mtDNA hypervariable regions 1 and 2, the sequence variants of MTCOI and MTCYB are helpful for individual identification with varied effectiveness in different population groups.