Question: A corporation has invented a new low-calorie sugar substitute. They want to determine if the substitute might be carcinogenic, so they use it in the Ames test with Salmonella his- mutants. The results show no increase in mutant bacterial colonies. They then perform feeding experiments in laboratory rats and find a significant increase in the incidence of cancer. Offer an explanation for why their original Ames test did not accurately predict the carcinogenic potential of the sugar substiture, and suggest a solution to the problem.