Comparison of the DNA's obtained from brain nuclei and mitochondria of mice and from the nuclei and kinetoplasts of Leishmania enriettii

Abstract DNA has been isolated from mouse-brain-mitochondrial preparations, free of nuclear contamination. After purification, the buoyant density and thermal denaturation profiles of this DNA have been compared with those of mouse nuclear DNA, and with the nuclear and kinetoplast DNA of Leishmania enriettii . The buoyant density of mouse mitochondrial DNA was 1.701 and its T m 82.8°. The C-G content was 42 %, calculated from the density, and 33 %, calculated from its T m . The buoyant density of mouse nuclear DNA was 1.702, and its T m 86.2°, corresponding to a C-G content of 43 % and 41 %, respectively. The buoyant density of the Leishmania kinetoplast DNA was 1.702, and its T m 83.0°, corresponding to a G-C content of 43 % and 33 %, respectively. The buoyant density of the Leishmania nuclear DNA was 1.721 and its T m 92.8°, corresponding to a C-G content of 62 % and 57 %, respectively. On thermal denaturation, the initial hyperchromicity of the two nuclear DNA's was approx. 25 %, that of mitochondrial DNA about 29 %, and that of kinetoplast DNA about 8 %. The degree of renaturation of mitochondrial DNA was 21.5 %, that of kinetoplast DNA 78.6 %. Mouse-nuclear DNA renatured 10.3 %, but Leishmania nuclear DNA 36.4 %. From these and other data it was concluded that the DNA from the protozoal kinetoplast was more homogeneous than protozoal nuclear DNA. Both protozoal DNA's appeared more homogeneous than mouse-mitochondrial DNA, whereas mouse nuclear DNA was the most heterogeneous. The data are consistent with the theory regarding the existence of mitochondrial inheritance.