Photoreactivation

Definition

Photoreactivation is a DNA repair mechanism where an enzyme called photolyase uses light energy to break the bonds of thymine dimers caused by UV radiation. This process restores the original DNA structure without excising nucleotides.

5 Must Know Facts For Your Next Test

1. Photoreactivation specifically repairs UV-induced thymine dimers in DNA.
2. The enzyme photolyase is activated by visible light, particularly blue and near-UV light.
3. This repair mechanism does not remove nucleotides but rather directly reverses the damage.
4. Photoreactivation is more common in prokaryotes but also occurs in some eukaryotes like yeast and plants.
5. It does not operate in dark conditions as it relies on light to activate photolyase.

Review Questions

Related terms

Thymine Dimers:

Covalent linkages between two adjacent thymine bases in DNA, often caused by UV radiation.

Nucleotide Excision Repair: A DNA repair mechanism that removes damaged sections of DNA and replaces them with the correct nucleotides.

DNA Photolyase: An enzyme that catalyzes the repair of thymine dimers using light energy during photoreactivation.