Answer:
Reverse mutations in the colonies enabled to recover the ability to synthesize histidine. The 2-aminoanthracene is a chemical agent that induce mutations and therefore it is potentially a carcinogen.
Explanation:
A reverse (suppressing) mutation is a type of mutation capable of restoring the activity of previously mutated genes. On the other hand, 2-aminoanthracene is an aromatic amine carcinogen capable of inducing hepatic and skin tumors. In this case, 2-aminoanthracene has been used to induce reverse mutations at loci responsible for the synthesis of histidine.
