The mitochondrial DNA(mtDNA) is a small extranuclear DNA molecule that has been sequenced in man. The mtDNA has distinct characteristics over nuclear DNA. First, the evolutionary rate of nucleotide substitution appears to be larger compared with the nuclear DNA. Second, mtDNA is maternally inherited, so the determination of the various haplotype is unequivocal and no recombination has to be involved. Third, there is a 1.1 kb long control region, which shows severe polymorphism. These characteristics have been applied for several evolutionary study. Furthermore, they exist in cytoplasm with numerous copy number and their size, 16,569 by is small relative to nuclear DNA, so they are more resistant to degradation or can be typed in samples with only cytoplasm such as hair shaft without hair root. These presented the possibility of mtDNA as a tool in individual identification, especially when the nuclear DNA be unavailable. Actually, polymorphism in control region has been applied to individual identification for the skeletal remain found in Vietnam war.
So we decided to apply the polymorphism of mtDNA in control region for the individual identification in case of mass disaster-"Downfall of Sampoong Department". Hu-man remains from total 27 different individuals and 178 control persons were submitted for the individual identification. As the mtDNA comparison could be done through maternal lineage, 12 individual from 9 families from the control group were ruled out, because these families were consisted of father or were seeking for their father. Sequencing for the mtDNA control region was done using ABI automatic sequencer and DyeDeoxy Terminator Cycle Sequencing Kit. For convenience, sequencing reaction was done for two separate control region, region I from 1601616401 in Anderson sequence, and region II from 048-388. First, sequences in region II of all samples and control persons were compared, and 20 samples were ruled out with no identical sequences in control group. Remaining 7 samples showed identical sequences with some of the control persons in three groups, and these identical pairs underwent mt DNA region I study. After region I study all samples except two dropped out in blood relation-ship. For the confirmation, STR and VNTR study such as MCT118, apoB, YNZ22, vWF, MBP, D21S11, TC-11 were done for remaining the two samples. The result denied the blood relationship between these two samples and any of the control group.
|