In a nutrient medium that lacks histidine, a thin layer of agar containing around 10^9 Salmonella typhimurium histidine auxotroph produces around 13 colonies over a two day incubation period at 37 degrees centigrade. How do these colonies arise in the absence of histidine? The experiment is repeated in the presence of 0.4 micrograms of 2-aminoanthracene. The number of colonies the number of colonies produced over 2 days exceeds 10,000. What does this indicate about 2- anthracene? What can you surmise about its carcinogenicity?

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.

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glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.