Interpretation of C tract in the D-Loop of Mitochondrial DNA.

Korean J Leg Med. 2002 Oct;26(2):42-50. Korean.

Department of Forensic Medicine, Chonnam National University Medical School, Korea.

National Institute of Scientific Investigation, Western District Office, Korea.

The D-loop of mitochondrial DNA contain C tracts(homopoymeric cytosines) in the positions of 16183 -16193, 303 -315, 568 -573 of GI 1944628 of NCBI. When the sequence of these positions are analyzed, the sequencing reactions or their signals after the C tract were abruptly decreased and cannot clarify the nucleotide signals in many cases. It is hard to characterize of the C tract. To characterize the C tract, we tried to analyze the sequence of clone and amp-length polymorphism with silver stain after amplification of small fragments including C tract of 16183 -16193 and 303-315.These results were compared with the results of characterization of nucleotides after separation of each nucleotide signal from the electropherogram which were increased in the Y axis to intensify the small overlapped signals using CHROMAS program. All methods we tried showed similar pattern of heteroplasmies of homopolymeric cytosines. Conclusively, it is not necessary to try resequencing reaction after cloning or amp-length polymorphism using silver stain. Intensification of the small overlapped signals in Y axis and separation of each signal is enough method to characterize the C tract.

Key Words : Mitochondrial DNA, C tract, Heteroplasmy