| Study on the Mutation Rate and Heteroplasmy for MtDNA Hypervariable Region. |
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Soong Deok Lee, Gi Beom Kim, Yoon Seong Lee, Jung Bin Lee |
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Department of Forensic Medicine, Seoul National University, College of Medicine, Korea. |
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| Abstract |
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The mtDNA hypervariable region is lymorphic and individual specific, sobecame one of useful markerws for individual identification. It is valuable es-pecially when traditional nuclear markers are unavailable in case of degraded materials, hair shaft without root, archaeological materials and so on. Many studies have revealed the general status of the polymorphism, but some points such as mutation rate and heteroplasmy must be clarified before its routine use in forensic science. For this family study was done for the mutation rate and heteroplasmy in the hypervariable region was verified in artificial mixed samples and autopsy materials. The simple and rapid sequencing technique-di-rect sequencing for the PCR product-was also tested. Usually the direct sequencing for the PCR product yield a good result. After cloned the PCR product, the sequenced length was somewhat longer about 20-30 bp especially near the primer and the succession rate was higher. but basically there was no difference between the direct sequencing and the colning of the PCR product. No mutation was noted through 101 mother-child pairs. In artificial mixed samples, when the ration of two different samples was be-tween 1:1 - 1: 7, the sequencing reaction tended to end abruptly and the back-ground noise was high with inappropriate sequence designation in automatic sequencer. But as the ratio riweto 1: 10 - 1: 2-, the reaction mimic as if there was no minor component, and it was hard to discern the minor component.No case which show any evidence of heteroplasmy by nucleotide substitution was noted'in 300 Koreans. Compared to this, heteroplasmy with length polymorphism was noted in re-gion I. If T-C transition occur in 189 Anderson site-this was noted in 47 / 306 (15.3%) of Koreans-, ten poly C sequence in 183- 192 is produced. For these samples the sequencing reaction ended abruptly. The length of poly C tract was variable from 9 to 13. Also the disrtribution of length variation was differ from person to person. And we found a case which showed heteroplasmy due to nucleotide substitution. For these samples repetitive reaction with cloning is recommended. And some guideline must be made for the routine use of mtDNA to circumvent the ambiguity of heteroplasmy. |
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