The combined use of amber mutations and an amber suppressor produces a conditional mutant, which is a mutant that is expressed under some circumstances but not under others. Conditional mutants are especially useful for studying mutations in essential genes. Another kind of conditional mutation is a temperature sensitive mutation for which the mutant trait is exhibited at high temperature but not at low temperature. In a sense,auxotrophic mutations are also conditional because auxotrophic mutants can be grown in the presence of the required nutrient but the mutants will not grow when the nutrient is not providedThe combined use of amber mutations and an amber suppressor produces a conditional conditional mutant, which is a mutant that is expressed under some circumstances but not under others. Conditional mutants are especially useful for studying mutations in essential genes. Another kind of conditional mutation is a temperature sensitive mutation for which the mutant trait is exhibited at high temperature but not at low temperature. In a sense, auxotrophic mutations are also conditional because auxotrophic mutants can be grown in the presence of the required nutrient but the mutants will not grow when the nutrient is not provided