GENE 540 Study Guide - Midterm Guide: Homologous Recombination, Homologous Chromosome, Dna Ligase
Document Summary
Single strand breaks not a big tissue as you can re-ligate the dna with ligase (this type of damage makes up 50% of daily damage) Double stranded breaks are rare (9 events per day), but much harder to deal with they can have serious consequences. They can be caused via radiation (gamma rays) and chemicals. Chemotherapy involves double stranded dna breaks generate so much damage that the mutated cells cannot fix themselves; but the problem with that is you are also causing damage to yourself. Example: the translocation shown requires a double stranded breaks; bcr-abl is an example. Non-homologous always losing dna; this is the main mechanism in higher organisms but it results in loss of base pairs at the joining sites and if the bases lost were important, then it could lead to mutations. Homologous recombination error free (the other chromosome is used as a template to fix the damage that was generated)
