Final answer:
The three DNA replication repair mechanisms in eukaryotes are Base Excision Repair, Nucleotide Excision Repair, and Mismatch Repair, which correct different types of DNA errors to maintain genetic stability.
Step-by-step explanation:
The three DNA replication repair mechanisms in eukaryotes are Base Excision Repair, Nucleotide Excision Repair, and Mismatch Repair. The general roles of these mechanisms ensure the fidelity of DNA replication and maintain genome stability.
- Base Excision Repair (BER) is used to fix minor DNA damage affecting single bases, often caused by oxidation, alkylation, or spontaneous loss. DNA glycosylases recognize and remove the damaged bases, followed by end processing and repair synthesis to fill in the gap, and finally, ligation to restore the DNA strand's integrity.
- Nucleotide Excision Repair (NER) is responsible for removing bulky, helix-distorting lesions, such as those caused by UV light, through the cutting out of a short single-strand DNA segment containing the lesion, followed by DNA repair synthesis and ligation.
- Mismatch Repair (MMR) corrects DNA replication errors that escape the DNA polymerase's proofreading activity, such as base-base mispairs and insertion-deletion loops. MMR identifies the mismatch, excises a section of the DNA strand containing the error, and fills in the correct nucleotides.