Changes in the structure of the DNA of Drosophila Melanogaster during development and aging

The DNA and RNA content of the fruit fly, Drosophila melanogaster under goes two cycles of synthesis and loss during the larval and pupal stages of development. The adult stages show little or no change with age in DNA content. Thermal melting curves, sedimentation velocities and CsC1 buoyant density measurements have been used to show that the molecular weight of larval DNA is of the order of 10-4 daltons. However, a fraction of the larval DNA (about 25%) is of a molecular weight greater than 10-6. Molecular weights increase during the later larval and pupal stages until a maximum of greater than 10-6 is reached during the adult stages. The molecular weight of embryonic DNA is greater than 10-6 but is rapidly degraded after hatching during early first instar larval development. Several interpretations of these data are offered. Buoyant densities in cesium salts showed no developmental or age-related changes.