Which process involves DNA polymerase proofreading for errors?

The correct answer is mismatch repair. This process specifically involves DNA polymerase proofreading and error correction during DNA replication. DNA polymerase has the ability to detect and correct mistakes in the newly synthesized DNA strand. When an incorrect nucleotide is added to the growing DNA chain, DNA polymerase can recognize the mismatch. It then excises the incorrect nucleotide and replaces it with the correct one, ensuring the fidelity of DNA replication.

Mismatch repair is part of a larger system that repairs errors that escape the proofreading activity of DNA polymerase. This makes the replication process more reliable and helps maintain the integrity of genetic information.

In contrast, excision repair involves the removal of damaged DNA segments but is not primarily about the proofreading capability of DNA polymerase itself. Gene expression pertains to the process by which information from a gene is used to synthesize functional gene products like proteins, while transcription is the first step in gene expression where RNA is synthesized from the DNA template. Neither gene expression nor transcription directly involves the proofreading mechanism employed by DNA polymerase during replication.