AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

PHOTOREACTIVATION

• It involves an enzyme that splits thymine dimers directly without the removal of any nucleotides.
• This enzyme will bind to thymine dimers in DNA in the dark, but it cannot catalyse the cleavage of the bonds joining the thymine molecules without energy derived from visible light specifically light within the blue region of the spectrum.
• The enzyme is also active on cytosine dimmers and cytosine-thymine dimmers.
• Thus UV light is used as an experimental mutagen, the treatment is usually carried out in the dark to maximise the mutation frequency.