Base excision repair — Flashcards

Flashcard 1: Which enzyme catalyzes the formation of a phosphodiester bond between Okazaki fragments?_____

Answer: DNA ligase

Flashcard 2: Which base excision repair enzyme is responsible for removing nucleotides at the 3' end?_____

Answer: Lyase

Flashcard 3: Xeroderma Pigmentosum is an inherited pathology due to a defective _____ pathway

Answer: Nucleotide Excision Repair

Flashcard 4: What form of DNA repair fixes mutations induced by UV radiation?_____

Answer: nucleotide excision repair

Flashcard 5: What process is used by mismatch repair enzymes to distinguish between old and new DNA strands in prokaryotes?_____

Answer: DNA methylation

Flashcard 6: What are the four mechanisms of DNA repair?

Answer: Nuceotide excision repair Base excision repair Mismatch repair Nonhomologous end joining

Flashcard 7: non-homologous end joining

Answer: join 2 dsDNA ends

Extra: double-stranded breaks (when no homologous chromosome is around to use as a guide)ataxia telangiectasia

Flashcard 8: mismatch repair

Answer: 1. new strand recognized (lacks methylation) 2. mismatched nucleotides removed 3. DNA pol/ligase fills/seals gap

Extra: Mismatched bases on newly synthesized DNA strandhereditary nonpolyposis colorectal cancer (HNPCC)

Flashcard 9: base excision repair (BER)

Answer: 1. specific glycosylases recognize and remove damaged bases 2. AP endonuclease removes AP DNA 3. DNA pol/ligase fill/seal gap

Extra: spontaneous/toxic changes to the base itself; most often deamination

Flashcard 10: nucleotide excision repair (NER)

Answer: 1. endonuclease removes short ssDNA segment containing lesion 2. DNA pol/ligase fill/seal gap

Extra: bulky adducts, commonly thymine dimers caused by UV radiation xeroderma pigmentosa