BB1720 DNA: damage and repair

Question 1

What are examples of how mutations in DNA can occur?

Answer 1

• Deletions (loss of nucleotide(s))
• Insertions (gain of nucleotide(s))
• Purine to purine - e.g. A to G
• Pyrimidine to pyrimidine - e.g. C to T
• Transversions - Purine to pyrimidine
• Transversions - Pyrimidine to purine

Question 2

what causes exogenous damage to DNA?

Answer 2

• Chemicals (e.g. hydrocarbons in cigarette smoke)
• ionising radiation (e.g. X rays)
• UV (sunlight)

Question 3

what causes endogenous damage to DNA?

Answer 3

• DNA replication errors
• Hydrolysis - water drives the reaction
• Oxidation

Question 4

what are DNA repair mechanisms?

Answer 4

• Base Excision Repair (BER)
• Direct repair
• Homologous recombination repair (HR)
• Mismatch Repair (MMR)
• Non-homologous end joining (NHEJ)
• Nucleotide Excision Repair (NER)
• Proofreading activity of DNA polymerase

Question 5

what is true about Non-homologous end joining (NHEJ) and Homologous recombination repair (HR)?

Answer 5

• HR is less error-prone NHEJ
• NHEJ is more error-prone HR