Revertante

Revertants, from lat. revertere = to return or turn around, are so-called reverse mutants. These are mutants in which a previous mutation was reversed by a new mutation(reverse mutation).

Revertants are those living beings whose ancestors have lost the ability to synthesize a vital substance through mutation, for example, but have regained this ability to synthesize through a renewed mutation.

Such remutations often occur spontaneously. Under certain environmental influences (presence of mutagenic substances) this rate can be greatly increased. This is exploited in the Ames test to check the mutagenicity of substances.