Final answer:
Mismatch repair is a DNA repair mechanism that corrects errors in DNA replication. Repair enzymes recognize mispaired nucleotides and excise the strand containing the error, which is then resynthesized. In E. coli, methyl groups help with recognizing the incorrect base.
Step-by-step explanation:
Mismatch repair is a DNA repair mechanism that corrects errors that occur during DNA replication. The repair enzymes recognize the mispaired nucleotide and excise the strand containing it. The excised region is then resynthesized, replacing the incorrect base with the correct one. This ensures that the DNA errors are returned to their original sequences. For example, in E. coli, methyl groups are added to the nitrogenous base adenine after replication, allowing the repair enzymes to recognize the incorrect base.