Nucleic Acids Research, 1975, Vol. 2, No. 2 197-210
© 1975
Articles |
Heterogeneity of mitochondrial DNA from Saccharomyces carlsbergensis, Denaturation mapping by electron microscopy
Institute of Medical Microbiology, University of Aarhus DK-8000 Aarhus C, Denmark
Received December 28, 1974. Electronmicroscopic observation of the denaturation pattern of 130 partially denaturated linear mitochondrial DNA molecules from Saccharomyces carlsbergensis was used to investigate the distribution of AT-rich sequences within the mitochondrial genome. The molecules were observed after heating to 43°C in the presence of 12% formaldehyde. These conditions resulted in an average denaturaticn per molecule of 21%. The average length of the molecules was 10 µm, and a few molecules had a length corresponding to the size of the complete genome. The undenaturated regions varied in length from 0.1 to 5.0 µm with denaturated regions of length 0.02 to 0.1 µm in between. A denaturation map was constructed by use of one of the long molecules (28.7 µm) as a master molecule for positioning of all other molecules. This map shows distinct regions corresponding to the position of easily denaturated sequences in the mitochondrial DNA. These sequences which presumably correspond to the very AT-rich regions, known to exist in the yeast mitochondrial DNA, were found at intervals of about 0.5 – 3 µm on the map.