Question

WHY DISTORTION ALONE IS NOT SUFFICIENT-

Identify the difference between the _________________________________, the repair would only be corrected 50% of the time by random chance.
The error rate (and therefore the __________________) would still be less than in a system that lacked the mismatch repair enzymes (1 mistake per ______________), but greater than the error rate in a system that accurately identifies the newly synthesizes strand (1 mistake per _______________.)

Answer 1

Mismatch repair is crucial for correcting replication errors by recognizing the new strand and replacing incorrect nucleotides. Without it, distortion alone would lead to much higher error rates, as repair would be less accurate and dependent on chance.

Step-by-step explanation:

The question deals with why distortion alone is not sufficient in DNA replication error correction, specifically focusing on the role of mismatch repair (MMR). Distortion refers to identifying incorrect nucleotides based on the misshapen pairing. However, it doesn't address which strand contains the error. Mismatch repair becomes crucial here, as it can correct errors after replication by recognizing the newly synthesized, non-methylated strand in bacteria like E. coli. Mutations in mismatch repair enzymes can lead to permanent damage, emphasizing the importance of accurate identification and repair for genome stability.

Without accurate mismatch repair mechanisms, the ability to identify and correct errors would rely on random chance. If repair enzymes could not distinguish between the old and new strands, then theoretically, they would correct errors correctly only 50% of the time. This would lead to a higher error rate compared to a system with precise mismatch repair. For example, in a less accurate system, the error rate might be 1 mistake per few hundred or thousand bases, whereas in an accurate system, it might be as low as 1 mistake per billion bases.