User:Agathman/CPDs Working Page
From Wikipedia, the free encyclopedia
Pyrimidine dimers are molecular lesions formed from thymine or cytosine bases in DNA via photochemical reactions.[1][2] Ultraviolet light induces the formation of covalent linkages by reactions localized on the C=C double bonds.[3] Two common UV products are cyclobutane pyrimidine dimers (CPDs, including thymine dimers) and 6,4 photoproducts. These premutagenic lesions alter the structure of DNA and consequently inhibit polymerases and arrest replication. Dimers may be repaired by photoreactivation or nucleotide excision repair, but unrepaired dimers are mutagenic. In humans they are the primary cause of melanomas.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/3/31/DNA_UV_mutation.png/320px-DNA_UV_mutation.png)