Tanaka M, Ozawa T
Department of Biomedical Chemistry, Faculty of Medicine, University of Nagoya, Japan.
Genomics. 1994 Jul 15;22(2):327-35. doi: 10.1006/geno.1994.1391.
Replication of mitochondrial DNA is highly asymmetric between the heavy (H) and the light (L) strands. The parental H strand is displaced by the daughter H strand and remains in a single-stranded state until the daughter L strand is synthesized. To examine the effect of this asymmetric replication on mutagenesis, we determined sequences of mtDNAs from 43 human individuals. Occurrence of nucleotide substitutions at 4-fold degenerate sites was distinctly asymmetric between the two strands: G-->A and T-->C transitions were 9- and 1.8-fold more frequent on the L strand than on the H strand, respectively. This nucleotide substitution bias is consistent with the T and G abundance of the H strand as well as the A and C abundance of the L strand.
线粒体DNA在重链（H）和轻链（L）之间的复制高度不对称。亲代H链被子代H链取代并保持单链状态，直到子代L链合成。为了研究这种不对称复制对诱变的影响，我们测定了43个个体的线粒体DNA序列。在4倍简并位点上核苷酸替换的发生在两条链之间明显不对称：L链上G→A和T→C转换的频率分别比H链高9倍和1.8倍。这种核苷酸替换偏向与H链的T和G丰度以及L链的A和C丰度一致。
