Repair of UV Damage

The sun gives off UV radiation that can damage DNA by inducing the formation of bonds between adjacent thymine bases. This type of damage is called a thymine dimer and causes a bulge to appear in the double helix, obstructing the normal DNA replication process and resulting in changes or mutations in the DNA sequence. However, UV damage can be repaired by special repair enzymes, including an endonuclease that excises the region of DNA containing the thymine dimer. Once the dimer has been removed, DNA polymerase fills in the gap with fresh nucleotides and another enzyme called DNA ligase seals the new segment of DNA into the repaired strand.

Question 1: UV radiation can damage DNA by forming _________ between adjacent thymine bases.
  1. Gaps
  2. Bonds
  3. Bridges
  4. Acceptors

Answer 1

Answer (b) - Bonds

Question 2: A thymine dimer causes a bulge to appear in the double helix, obstructing the DNA replication process, and causing _________ in the DNA sequence.
  1. Mutations
  2. Bumps
  3. Repair
  4. Breaks

Answer 2

Answer (a) - Mutations

Question 3: Once the thymine dimer has been removed by special repair enzymes and polymerase has filled the gaps with fresh nucleotides, DNA _________ seals the repaired strand.
  1. Exonuclease
  2. Endonuclease
  3. Ligase
  4. Transferase

Answer 3

Answer (c) - Ligase