CIRCULAR MITOCHONDRIAL DNA FROM XENOPUS LAEVIS AND RANA PIPIENS

Mitochondrial DNA from oocytes of Xenopus laevis and Rana pipiens and from the liver of Gallus domesticus was studied by electron microscopy using the Kleinschmidt technique [osmotic shock]. A high percentage of circular molecules, either highly twisted or open, was observed in all preparations. The mean contour length of circles fromX. laevis was 5.40 [mu], from R. pipiens 5.56 [mu] and from G. domesticus 5.26 [mu]. Highly twisted circles were found in greater abundance in a fresh preparation than in preparations left standing for 3 months. These molecules are considered to be the native form of mitochondrial DNA.