Answer to Question 1 from November, 2002

1. (4 points) In a few words, please list the types of DNA damage that are repaired by each of the major excision repair pathways: (a) mismatch repair (MMR), (b) base excision repair (BER), (c) nucleotide excision repair (NER).

  1. Replication errors. This includes base-pairing mismatches, small deletions and small insertions.
  2. Damaged bases (including alkylated bases and oxidized bases), base loss (AP sites), and certain mismatched bases.
  3. Any damage that both significantly distorts the structure of the DNA molecule and significantly alters its chemistry. This includes most of the photoproducts produced by UV irradiation, including cyclobutane pyrimidine dimers and 6-4 photoproducts.

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