A break is induced by radiation at a corresponding point in both complementary strands of a DNA molecule. The bond broken is between the base and the sugar molecule to which it is attached. Thus two complementary bases (held together by hydrogen bonds) are detached from their backbones. If the pair rotates before it is reinserted in the molecule, the resulting transversional mutation would be termed a rotational base substitution. Many radiation-induced point mutations may result in this way.
Subjects: Genetics and Genomics.