Colony survival assay.

For studies of DNA repair networks the sensitivity of mutants and combinations of mutants to varying forms of DNA damaging agents has formed a mainstay of genetic analysis in bacteria and yeast. Likewise, this form of epistasis analysis has proved immensely informative in DT40. Because DT40 is non-adherent, it is necessary to restrict the movement of cells by growing them in a viscous medium containing methylcellulose. Here we present methods for carrying out DNA damage survival assays in DT40 with chemical mutagens, ionising radiation and ultraviolet irradiation.