PSY 005 Lecture Notes - Lecture 8: Damage Tolerance, Antigen, Thymine

• School: College of The Sequoias
• Department: Psychology (PSY)
• Course: PSY 005
• Professor: Jibai

Document Summary

Uv light is a non-ionising radiation that induces two predominant lesions: Ultraviolet radiation light: cyclobutane pyrimidine dimers, 6,4-photoproducts. Pyrimidine dimers are molecular lesions formed from thymine or cytosine bases in dna via photochemical reactions. Ultraviolet light induces the formation of covalent linkages by reactions localized on the c=c double bonds. In dsrna, uracil dimers may also accumulate as a result of uv radiation. 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. A cyclobutane pyrimidine dimer contains a four membered ring arising from the coupling of the c=c double bonds of pyrimidines. Such dimers interfere with base pairing during dna replication, leading to mutations. 6,4-photoproducts, or 6,4 pyrimidine-pyrimidones, occur at one-third the frequency of cyclobutane pyrimidine dimers but are more mutagenic. The nucleotide excision repair system provides the cell"s ability to remove bulky lesions from dna.