Circular Dna Molecules Associated with Chloroplasts of Spinach, Spinacia Oleracea

Results of cytochemical studies (Sagan and Scher, 1961 ; Ris and Plaut, 1962 ; Kislev et al ., 1965) and of studies involving cell fractionation and buoyant density analyses (Sager and Ishida, 1963 ; Ray and Hanawalt, 1964 ; Brawerman and Eisenstadt, 1964 ; Edelman et al ., 1964 ; Wells and Birnstiel, 1969) have shown that chloroplasts of microorganisms and of higher plants contain DNA which is distinct from that of the nuclear DNA of these organisms. We have recently presented evidence that chloroplast DNA of the protozoan flagellate, Euglena gracilis is in the form of circular molecules about 40,u in contour length (Manning et al ., 1971) . Evidence presented in the present report indicates that circular DNA molecules, approximately 44 μ in contour length, are associated with chloro-