How does radiation therapy kill cancer cells?

• A. By enhancing their repair mechanisms
• B. By cutting DNA and causing irreparable mutations
• C. By supplying nutrients to the cells
• D. By freezing the cells

Answer: (B)

Radiation therapy effectively kills cancer cells primarily by damaging their DNA. The high-energy radiation used in this treatment generates free radicals that can directly cut through the DNA strands or cause other forms of damage, leading to mutations. When cancer cells are exposed to radiation, their ability to repair this damage is often overwhelmed, especially because many cancer cells are less efficient at DNA repair compared to normal cells.

If the damage to the DNA is extensive and the cell cannot effectively repair it, this can trigger apoptosis, or programmed cell death. Therefore, the primary mechanism by which radiation therapy exerts its effects is through the induction of irreparable mutations in the cancer cells' DNA, effectively preventing them from continuing to proliferate and survive.

The other options do not accurately reflect the mechanisms of radiation therapy. Enhancing repair mechanisms would potentially make cancer cells more resilient, while supplying nutrients or freezing the cells does not directly contribute to the killing of cancer cells through radiation treatment.