In this lab simulation students conduct a modified Ames Test, which predicts carcinogenicity of chemicals. Students are provided with a virtual strain of Escherichia coli that is sensitive to (killed by) the antibiotic streptomycin, several virtual chemicals to test for mutagenicity, and two types of media (nutrient Agar and nutrient Agar + Streptomycin). The simulation allows students to propose a hypothesis about the types of chemicals that are likely to be mutagens and design an experiment to test their hypothesis.