Polymorphisms and Mutations of the Mitochondrial DNA D-loop in the Maternal Genetic Lineages

Yoon, Seo Ra; Lee, Young Jik; Park, Jong Tae

Abstract

To investigate the polymorphisms of the mitochondrial DNA (mtDNA) D-loop and the mutation rates in the maternal lineages in Koreans, the sequence of mitochondrial DNA D-loop was analyzed in the 140 maternally unrelated individuals and 43 families consisting of 108 individuals. The mtDNA D-loop was amplified from 15909F to 600R according to the Anderson's standard sequence, followed by direct sequencing for the PCR product using ABI Prism 310 automatic sequencer. Totally 283 variation sites were noted compared with Anderson sequence, among which 143 sites (50.5%) were in Hypervariable Region (HVR) I, 97 sites (34.3%) in HVR II, and 43 sites (15.2%) in non-HVR I and II. These polymorphic sites were distributed relative evenly in the whole D-loop. Nucleotide substitution was the most frequent anomaly as seen in 88.4%, insertion occurred in 8.6%, and deletion in 3.0%. Among all the changes, the major patterns of variation were T->C (26.0%), A->G (24.6%), and C->T (22.8%). The mutation patterns of "C" chain were observed in 32 types and they may play a role in identifying independent genotype. The mutations were observed in 20 families; it was found that each family ordinarily presented with one or two mutation sites, which had low frequencies of variations in the analysis of polymorphisms in the maternally unrelated 140 individuals. The maximum rate of mutation detected in this study was 6. The mutation sites were not limited to the hypervariable region I or II. Conclusively, full sequence of mitochondrial DNA D-loop is necessary for individual identification, because the sites of variations and mutations are not limited to the hypervariable region I and II.