Which one of the following contributes to the utility of the strains of Salmonella typhimurium used in the Ames reversion assay?
A. They are highly permeable to test substances.
B. It is very straightforward to assay the conversion of their histidine auxotrophy mutations to histidine prototrophy.
C. They are defective in DNA repair and, therefore, cannot readily repair damage done by the test substances.
D. All of the choices are correct.
Answer: A
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