LAB 4 WORKSHEET

LAB WORKSHEET FOR LAB 4: UV Mutagenesis, Survivorship Analysis, and Screening for Defective Lactose Metabolism in E.coli NAME: Ashleigh Bonanno LAB SECTION: 02 Tuesday This worksheet is DUE AT THE BEGINNING OF YOUR WEEK 5 LAB SECTION. Type all answers clearly in non-bold-face font under each question. You may work with others to discuss HOW to answer the questions, but the work you present must be your own. Using your count of survivorship for your mutagenized cell culture, estimate the percent survival of your sample. Your instructor will have provided the cell counts for the un-mutagenized sample. If you had no growth on your plates, use someone else’s non-zero data for this calculation and be sure to point out who’s data you are using. (25 points) (10/ 171000000)x 100 = 5.85 x 10-6 % For the lab section data, generate a survivorship curve for your mutagenesis experiment. Your TA should provide a spreadsheet that includes the class’s data. Calculate the survival ratio for each replicate. Plot mean survivorship (with standard errors) as a function of exposure time. Be sure to follow SMCM style guidelines for the formatting of your figure.(50 points) Figure 1: Mean survivorship of colony forming units as a function of exposure time in seconds Briefly describe the results shown in your figure. What biological conclusions can you draw from this experiment? What UV exposure treatment would you recommend for our mutagenesis experiments? (25 points) This figure shows a decreasing relationship between time exposure and survival percentage. This tells us that when bacteria that lack a DNA repair function and are exposed to UV light for prolonged time, the cells colonies die and will not further replicate. This figure can also be used to interpret optimal conditions for Lac-phenotypic mutants, which is less than 30 seconds of exposure to UV light. I would recommend a UV exposure between 10 and 30 for our mutagenesis experiment because that range is the only range where colonies will still live/grow.