期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：11
页码：6415-6419
DOI：10.1073/pnas.77.11.6415
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Restriction enzyme analysis of mtDNAs for the purpose of determining sequence divergence rests on the assumption that variant recognition sites differ with respect to sequence and not methylation. This assumption was tested on two mtDNAs, A and B, which are distributed throughout the laboratory rat population and which can be distinguished by a number of restriction enzymes. The mtDNAs were cloned and the nucleotide sequences of corresponding small HindIII fragments, in which a variant EcoRI site occurs, were determined. Evidence that the fragments differ in sequence and not methylation is as follows: (i) The cloned mtDNA yielded the same fragment pattern as did native mtDNA when treated with EcoRI, Hha I, HinfI, and Hae III; (ii) three nucleotide replacements were found in the 169-base pair fragment, A.T in equilibrium G.C, A.T in equilibrium G.C, T.A in equilibrium G.C; (iii) one of these replacements, A.T in equilibrium G.C at position 80, accounts for the presence of the EcoRI site in the type A and its absence in the type B mtDNA. Examination of the sequence leads to the suggestion that these three nucleotide replacements are silent; i.e., they would not lead to amino acid substitutions in a possible encoded protein.
