ABSTRACT
Parameterised linear–quadratic dose–effect equation for the induction of deoxyribonucleic acid (DNA) double strand breaks by ionising radiation is derived using the known structure and properties of the DNA molecule in eukaryotic cells. A double strand break can be induced as a consequence of one ionising radiation track breaking both strands of the DNA double helix, giving a yield of breaks in proportion with radiation dose. The repair of both DNA single strand breaks and DNA double strand breaks can influence the number of double strand breaks which are induced and remain biologically effective. Both repair processes depend on the metabolic activity of the cell, the cell stage and the time available for repair. The repair of single strand breaks is efficient and error-free because the nucleotide bases on the undamaged DNA strand can be used by the repair enzymes to reconstruct the broken strand, according to the complementary base-pairing rules.
