What process repairs damage to a preexisting double helix? See Concept 16.2 (Page) ? proofreading ? operon repair ? nucleotide excision repair ? mismatch repair transformation
The Correct Answer and Explanation is:
The correct answer is mismatch repair.
Mismatch repair is a crucial cellular process that repairs damage to a preexisting double helix, specifically correcting errors that occur during DNA replication. These errors typically include incorrect base pairing, where one nucleotide is mistakenly paired with another that does not belong in that position (for example, adenine paired with cytosine instead of thymine).
The process begins immediately after DNA replication, where the newly synthesized strand is checked for mistakes. The mismatch repair system can distinguish the newly synthesized strand from the older, original strand, often based on the presence of nicks or other marks in the newly synthesized strand. Proteins involved in mismatch repair, such as MutS and MutL (in bacteria), or their homologs in eukaryotes, are responsible for detecting these mismatches. Once detected, the erroneous section of the DNA is excised (cut out) and replaced with the correct nucleotide sequence using the correct strand as a template.
In addition to base pair mismatches, the mismatch repair system also plays a role in correcting small insertion or deletion loops that can occur during replication. This is an important process because if left unrepaired, mismatches can lead to mutations, which may contribute to diseases like cancer.
This repair mechanism is different from other repair processes such as nucleotide excision repair, which repairs large lesions (such as thymine dimers caused by UV radiation) by excising a segment of the DNA strand and filling in the gap. Meanwhile, operon repair typically refers to the regulation of gene expression in prokaryotes, and proofreading refers to the activity of DNA polymerases that check for errors during DNA synthesis, but do not correct mistakes after replication.
