The satellite bands of the DNA of Drosophila virilis

Purified DNA has been prepared from Drosophila virilis using a modification of the method derived for bacteria (Marmur, 1961). Some physical properties have been examined, a new hidden satellite discovered, and a difference found in the satellite banding pattern of different tissues. — In addition to the three satellite bands lighter than the main band previously reported (Gall et al., 1970), a new satellite heavier than the main band has been detected after thermal denaturation of the DNA (which substantially shifts the buoyant density of the main band but not that of the satellites indicating that all are fast-annealing). The satellite pattern of DNA extracted from heads alone differed from that of the entire animals: the amount of satellite I was decreased and II increased; III was unaffected; IV was increased relative to the amount in the main band. The total content of satellite material in the heads (assumed to be entirely diploid) was 42%, the highest amount reported for any organism. — Thermal transitions were determined for the DNA from adults and larvae. After preparative CsCl density gradient fractionation of adult DNA, two sets of bimodal thermal curves were obtained (in SSC) with agreement between the initial position in the preparative gradient, the thermal transitions, and the G+C content from density except for satellite III for which the T_m gave a more accurate G+C amount. DNA from satellites I and II together generated a T_m of 81.2° which was similar to a calculated T_m of 81.9° making the naive assumption that the thermal components of the two satellites would interact in a simple additive fashion. A T_m of 71.9° was ascribed to satellite III which indicates that it is not the equivalent of the poly (A-T) band found at the same density in D. melanogaster (Fansler et al., 1970). The calculated overall base composition from the density equivalents (using the value for satellite III from thermal data) gave an expected G+C content of 36.6%. The measured value was 36.0%. The possible significance of the differential satellite pattern has been discussed.