Survival of control strains and new haploid DSB repair mutants when EcoRI is expressed in vivo from a galactose-inducible promoter. (A) Colony forming ability and cell growth rate are reduced in recombination-deficient rad50, rad51 and rad52 mutants. (B) Example of pronging plate assay used to screen MATα library mutants for EcoRI sensitivity. Cells contained either vector (pRS316) or YCpGal::RIb. Cells grown in raffinose media were serially diluted 5-fold and pronged onto plates containing either raffinose or galactose.