Mutant ZFRs selected for recombination of Zcas2Z or Zcas5Z sites.

The Table shows mutants isolated from libraries of mutagenized ZFR300. The left-hand column gives the mutations, and the next column indicates the number of independent isolates. The other columns show the phenotype of each mutant in the MacConkey agar colony colour assay, using substrates with two identical ZcasZ sites as indicated. W, ‘white’ (pale-coloured) colonies; R, red colonies; M, mixtures of pale and red colonies. The letters in bold show the ZcasZ substrate (Zcas2Z and/or Zcas5Z) that was used in the screen from which the mutant was isolated. The four point mutants shown below the thick line were isolated by cloning appropriate fragments from the originally isolated multiple mutant (above the line). n.d., not done.