THE SPECIFICITY OF BASE-PAIR SUBSTITUTION INDUCED BY THE MUTL AND MUTS MUTATORS IN ESCHERICHIA-COLI

The E. coli mutator alleles, mutL and mutS, produced transversion as well as transition base-pair substitutions with the trpA reversion system. Transversions were generally mutator-induced at a lower level than transitions and the specific type of transversion and its nucleotide position appeared to strongly affect its level of enhancement. These results are interpreted to mean that mutL- and mutS- dependent mismatch correction is generally more effective at correcting transition mispairing than transversion mispairings. Correction of transversion mispairings is probably dependent upon site of occurrence and type of mismatch.