1. How would you isolate a lacl- cell that had a nonsense UAG mutation? Nonsense mutants have names UAG nonsense UAA nonsense UGA nonsense amber ochre opal Begin your selection with lacl+ cells. This cell also has an extra serine tRNA gene, whose anticodon has been mutated such that it is an amber suppressor, meaning it has an anticodon that will read a 5'-UAG stop codon. This extra serine tRNA gene is only expressed (ON) when cadmium ions are added: with NO cadmium ions this extra serine tRNA gene is not expressed (OFF). You may find it useful to be able to turn on and off this serine tRNA amber suppressor gene by either adding cadmium or by leaving cadmium out of the selection. lacl- amber mutants pre- exist in the culture at a low frequency (-10*) compared to the starting cells, which are wild type lacl+. Your answer should demonstrate that you understand the five formal steps for doing a mutational selection as described in class. For grading purposes your answer must be presented EXACTLY as I always do in class using a grid with the following type of format. reasoning either above or below this grid. Explain your 2. Ultimately, your plate will contain many colonies. Do you think that each of those colonies will have an amber mutation at the same amino acid position in lacl? Explain. 3. Would you expect your selection procedure to be able to select all amber (UAG nonsense) mutations in lacl or not? Explain.