Final answer:
The true statement about the Ames test is that it assesses the mutagenic potential of compounds using auxotrophic bacterial strains. It involves exposing bacteria to a test compound and then monitoring their growth on a medium lacking an essential nutrient, to see if mutations that reverse the nutrient requirement occur.
Step-by-step explanation:
True Statement Regarding the Ames Test
The statement from the options provided that is true regarding the Ames test is: It assesses the mutagenic potential of compounds using auxotrophic strains. The Ames test utilizes a strain of Salmonella typhimurium that requires histidine to grow due to a previous mutation that made it an auxotroph. These bacteria are exposed to the compound in question and then plated on a medium lacking histidine. If the compound is a mutagen, it may cause mutations that revert the histidine requirement, thus enabling the bacteria to grow. The number of colonies that grow indicates the mutagenic potential of the test compound. Additionally, because some chemicals become mutagenic after being metabolized, a rat liver extract is often added to simulate human metabolism.
The Ames test is used as a preliminary screen for the carcinogenic potential of chemicals because there is a correlation between mutagenicity and carcinogenicity. Although not definitive and subject to false-positives and false-negatives, it is a valuable tool for indicating potential cancer risks associated with chemical exposure before conducting more extensive testing in animal models.