FIGURE 3: Schematic representation of the yeast functional assays for MMR genes. Forward mutation frequency/rate is evaluated by scoring the number of colonies becoming resistant to (A) Canavanine (CAN1 to can1) or (B) 5-fluoroorotic acid (5-FOA, URA3 to ura3). Reverse mutation is assessed by counting the number of colonies becoming able to grow in selective medium lacking threonine (C) (THR+; hom3-10 to HOM3), (D) colonies becoming blue (lacZ to LACZ), (E) colonies becoming green (gfp to GFP), (F) colonies becoming white in medium lacking adenine (ADE+; ade2 to ADE2), (G) colonies becoming able to grow in medium lacking lysine (LYS+; lys2 to LYS2) and (H) colonies becoming able to grow in medium lacking histidine (HIS+, hys7-2 to HIS7). The URA3 gene used for forward reversion (B) contains an in-frame insertion of several nucleotides, therefore the gene is WT. Constructs of D, E, F and G contain out-of-frame insertion of several nucleotides, therefore the gene is mutated. Constructs of C and H contain a point mutation. Above the arrow are given the names of the human proteins studied with the assay.