The following set of three separate experiments was conducted. Two strains of Escherichia coli are used. Strain 1 needs histidine added to the medium to grow. Strain 2 needs methionine added to the medium to grow. (8 points) Experiment 1: After strain 1 and strain 2 are mixed in a culture flask containing a minimal medium (containing no added amino acids) and allowed to grow overnight. Results: It is possible isolate new strains that grow on the minimal medium. Experiment 2: Strains 1 and 2 are mixed in a culture flask containing a minimal medium but also containing the enzyme DNAse and grown overnight. Results: It is NOT possible isolate new strains that grow on the minimal medium. Experiment 3: Media is placed in a U-shaped tube that contains, at the bottom, a membrane filter that prevents cells from crossing between the two chambers of the U-tube, but allows anything small (for example DNA and bacteriophages) to pass between the chambers. The strains are put in different sides of the U-tube. Results: It is possible to isolate new strains that grow on the minimal medium. Conclusions: Genetic exchange is observed in experiments 1 and 3, but not experiment 2. 1. Why was Experiment 1 performed? What information does it give us? 2. Why was DNase added in Experiment 2? 3. What is the purpose of the U-shaped tube in Experiment 3? 4. Taking the evidence from all three experiments together, what type of genetic exchange was observed from these strains?