Question

Before the DNA repair enzyme complex has completed its function, approximately how many base pairs are still improperly matched?

Options

• 1 in 100,000

• 1 in 1,000,000

• 1 in 10,000,000

• 1 in a billion

Answer 1

1 in 100,000

Explanation:

Before the DNA repair enzyme complex (specifically, mismatch repair) completes its function, the error rate of DNA replication is approximately 1 in 10 million (10⁷) base pairs. This initial high level of accuracy is primarily due to the proofreading capability of DNA polymerase, which detects and corrects most mismatches as they occur. Once the specialised mismatch repair enzymes finalise their work, they reduce the error rate even further, by about 100 to 1,000 times, resulting in a final accuracy of roughly 1 in a billion (10⁹) base pairs.