Genetic and physical properties of unintegrated donor DNA molecules during Hemophilus transformation

Characteristics of the irreversibly-bound, unintegrated donor DNA molecules in Hemophilus transformation were analysed by sedimentation through sucrose gradients. Two unintegrated species of DNA molecule were recoverable: species I sedimented at the same rate as the original transforming DNA, and species II at a somewhat slower rate. Species II appeared to be somewhat heterogeneous. The faster-sedimenting DNA (species I) was biologically active but the slower-sedimenting DNA (species II) was practically devoid of biological activity. As a function of time following interaction between donor DNA and recipient cells, the species I decreased and species II increased. Species II molecules presumably arise as by-products in the process of integration.