DNA damages and corresponding repair mechanisms. Various exogenous and endogenous DNA damaging agents attack the DNA on a daily basis. As a result many different types of DNA lesions are generated (green DNA strand with marked damage types (red or written) and green boxes with names of damage types). In order to survive, the cells harbor a set of repair pathways (blue boxes). Important players mutated or misregulated in both canine and human cancers are depicted in the lower part.