Isolation and characterization of a linear DNA molecule in the fungus Ascobolus immersus

A plasmid-like DNA molecule was isolated from the fungus Ascobolus immersus in strains which exhibited genetic instability. It was found to be inherited maternally. The molecule had a density of 1.708 g/cc and a molecular weight of 4.1×106 daltons. Digestion simultaneously by two restriction enzymes demonstrated the linearity of the molecule. Electron microscopy of alkaline-denatured and self-renatured molecules revealed that the ends are inverted repeated sequences, 1200 base pairs in length.