Which term describes the effect when radiation directly ionizes the DNA of a cell?

Which term describes the effect when radiation directly ionizes the DNA of a cell?

• A. Direct Effect
• B. Indirect Effect
• C. Somatic Effect
• D. Genetic Effect

Answer: (A)

Direct effect happens when the radiation interacts with the DNA itself, depositing energy directly into the DNA molecule and causing ionizations that can lead to strand breaks and other lesions. This is the mechanism where the target is the DNA, rather than molecules around it. In contrast, the indirect effect involves the radiation first ionizing water in the cell, producing free radicals that then damage DNA. The other terms describe broader outcomes: somatic effects affect the irradiated person’s body, while genetic effects refer to changes in germ cells that can be passed to offspring. So, direct ionization of DNA is the direct effect.

Direct effect happens when the radiation interacts with the DNA itself, depositing energy directly into the DNA molecule and causing ionizations that can lead to strand breaks and other lesions. This is the mechanism where the target is the DNA, rather than molecules around it. In contrast, the indirect effect involves the radiation first ionizing water in the cell, producing free radicals that then damage DNA. The other terms describe broader outcomes: somatic effects affect the irradiated person’s body, while genetic effects refer to changes in germ cells that can be passed to offspring. So, direct ionization of DNA is the direct effect.