Which process uses an undamaged strand of DNA as a guide for repair?

Nucleotide excision repair is the process that specifically uses an undamaged strand of DNA as a template to accurately repair damaged DNA. This mechanism is vital for the maintenance of genetic integrity, as it recognizes and removes damaged nucleotides, which could result from environmental factors such as UV radiation or chemical exposure. The undamaged strand serves as a guide, allowing the repair machinery to replace the removed nucleotides through a series of steps that intend to restore the original sequence.

During nucleotide excision repair, enzymes recognize the distortion in the DNA structure caused by the damage, excise a short segment of the DNA strand that includes the damaged nucleotides, and then fill in the gap using the undamaged strand as a template. This detailed repair process ensures that genetic information remains stable and reduces the risk of mutations.

In contrast, DNA replication involves copying an entire strand of DNA and does not specifically focus on repairing damage; DNA ligation refers to the joining of DNA fragments and does not directly relate to repair; and protein synthesis pertains to translating genetic information into proteins, which is a different aspect of molecular biology. Therefore, nucleotide excision repair is the correct process that utilizes an undamaged DNA strand for its repair actions.