Question

match the following dna repair mechanism with the mutation they correct: question 8 options: 2 base excision repair 1 nucleotide excision repair 3 photoreactivation 1. thymine dimer 2. chemically modified bases 3. bulky dna lesions

Answer 1

Nucleotide excision repair fixes thymine dimers, base excision repair handles chemically modified bases, and photoreactivation corrects bulky DNA lesions like thymine dimers.

Step-by-step explanation:

The student's question pertains to the matching of DNA repair mechanisms with the types of mutations they correct. There are multiple mechanisms for repairing DNA, and three of them are being questioned here.

• Nucleotide excision repair is often employed when UV exposure causes the formation of pyrimidine dimers, such as thymine dimers. Enzymes make cuts on both the 3' and 5' ends of the damaged site, remove the affected segment, and the gap is then filled with the correct nucleotides by the action of DNA polymerase and sealed by DNA ligase.
• Base excision repair recognizes chemically modified bases such as oxidized, deaminated, or incorrectly paired bases. Specific enzymes excise the incorrect base and fill in the gap with the correct nucleotide.
• Photoreactivation is a light-dependent process that directly reverses the formation of thymine dimers. It is facilitated by the enzyme photolyase which, in the presence of visible light, breaks apart the dimer.

So, matching the repair mechanisms with the types of mutations, we have:

1. Nucleotide excision repair: thymine dimers
2. Base excision repair: chemically modified bases
3. Photoreactivation: bulky DNA lesions