Direct repair mechanisms — Flashcards

Flashcard 1: Chronic exposure to Arsenic may cause cancer by metabolites (ex. Dimethyl-Arsenic) inhibiting _____ motifs in Base-Excision Repair and Nucleotide-Excision Repair enzymes

Answer: zinc finger

Flashcard 2: What form of DNA repair fixes mutations due to spontaneous/toxic deamination?_____

Answer: Base excision repair

Flashcard 3: What mutation is induced by UV radiation?_____

Answer: Pyrimidine dimers (e.g. thymine dimers)

Flashcard 4: What process is used by mismatch repair enzymes to distinguish between old and new DNA strands in prokaryotes?_____

Answer: DNA methylation

Flashcard 5: What form of DNA repair fixes mutations due to DNA replication errors?_____

Answer: mismatch repair

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