What term describes destructive changes in molecules resulting when radiation acts directly on a target such as DNA?

• A. Radiochemolysis
• B. Direct effect
• C. Indirect effect
• D. Radio dystrophy

Answer: (B)

Destructive changes in molecules caused by radiation that acts directly on the target such as DNA are described by the direct effect. In this process, energy from the radiation deposits directly into the DNA, causing ionization and breaking chemical bonds, leading to strand breaks or cross-links. This is different from the indirect effect, where radiation first interacts with water to produce free radicals that then damage DNA. Indirect effect is typically more prominent with low-LET radiation, while direct effect is more associated with high-LET radiation. Other terms like radiochemolysis or radio dystrophy aren’t standard descriptors of this direct interaction.