Non-repair of a DNA strand break can lead to which outcomes?

• A. automatic repair
• B. repair without negative effects
• C. mutation, carcinogenesis, or cell death
• D. immediate repair

Answer: (C)

When a DNA strand break isn’t repaired, the genome becomes unstable and error-prone processes can copy or join the ends incorrectly as the cell cycles. This often produces mutations. If those mutations affect genes that control cell growth or genome integrity, they can accumulate and drive the development of cancer (carcinogenesis). If the damage is too severe or persistent, the cell may also trigger programmed cell death to prevent passing on damaged DNA. So leaving a strand break unrepaired can lead to mutations, carcinogenesis, or cell death.

The other ideas imply the break would fix itself without consequence, which isn’t supported by biology. Automatic repair or repair without negative effects would require successful, error-free correction, which is not guaranteed when the break is not repaired. Immediate repair isn’t applicable if you’re discussing non-repair scenarios.