Chloroplast DNA from Tobacco Leaves

Abstract

DNA from tobacco leaf chloroplasts was isolated as a single component with a buoyant density in CsCl of 1.702 compared to 1.697 for nuclear DNA. 5-Methylcytosine is present in nuclear DNA but absent in chloroplast DNA. Chloroplast DNA, with a guanine-cytosine content of 43 percent, has a melting temperature of 86°C and renatures completely on slow cooling, whereas nuclear DNA ( melting temperature, 84°C; guanine-cytosine content, 40 percent) does not renature. About 9 percent of the total DNA in tobacco leaves is chloroplast DNA representing about 4.7 xX 10-¹⁵ gram of DNA per chloroplast with a molecular weight of approximately 4 xX 10⁷.