Sarah's Assignment

I'm interested in the DNA repair mechanisms our species might have. Since or species is in such exposed conditions, how does it evade the mutational effects of UV light?

Commonly found UV-mediated mutations are cyclobutane dimers (pyrimidine dimers) and 6-4 photodimers.

Cyclobutane dimers consist of either C=C binding or T=T binding. UV light creates covalent bonds between adjacent thymidines or cytosines,which can inhibit transcription or replication of DNA. Cytosines that are part of a dimer are also more likely to be deaminated and changed to uracil. This can cause errors in either transcription or replication [1] [2].

Deoxyribodipyrimidine photolyases are partially responsible for correcting cyclobutane dimers by breaking the covalent bonds formed by UV light exposure. The reaction they perform can be characterized by: cyclobutadipyrimidine (in DNA) = 2 pyrimidine residues (in DNA) [3].