3. Cellular response to DNA damage Reponse Mechanisms Tolerance of DNA damage Replicative bypass of template damage Translesion DNA synthesis Reversal of DNA damage Enzymatic photoreactivation Repair of O 6 -alkylguanine, O 4 - alkyltimidine Ligation of DNA strand breaks Excision of DNA damage Base Excision Repair Nucleotide Excision Repair Mismatch Repair Double strand breaks ligation Single strand annealing Recombinational Repair Non-Homologous End Joining

7. La radiazione Solare può essere distinta in 3 componenti principali a seconda della lunghezza donda: ULTRAVIOLETTO (100-400 nanometri) 10% VISIBILE ( 400-750nm.) 45% INFRAROSSO (750-3000nm.) 45%

8. UV-induced damage

10. UV-responsive photolyases

11. Direct reversal (de-alkylating proteins)

12. Base Excision Repair

15. Nucleotide Excision Repair (E.coli)

17. Nucleotide Excision Repair (Global Genome Repair -Humans)

18. Nucleotide Excision Repair (Transcription Coupled -Humans)

19. Common features of GGR & TCR