Figure 2.

Schematic representation of the screen. A diploid double mutant elg1Δ srs2Δ strain is kept alive by the presence of a plasmid carrying the ELG1 gene. The ADE3 marker on the plasmid confers a red pigment to the cells carrying it (as the strain is ade2 ade3). Since any cell that loses the plasmid during colony formation dies, all colonies are uniformly red. This strain was transformed with a high copy number library carrying random fragments of the yeast genome. Cells that received a plasmid that suppresses the SL phenotype (SUPP1) can now lose the ELG1-containing plasmid, becoming white. These cells create white or red/white sectored colonies.