WORKSHEET QUESTIONS 2 (Total: 16 marks) Due May 26 by 2:30 pm EST 1. Experiment: You have introduced a plasmid expressing kanamycin resistance into E. coli host cells. To identify cells that have taken up the plasmid, you need to plate the transformation mix on solid media supplemented with the antibiotic, kanamycin. Your supervisor suggests the following controls. Indicate 1) what each control tells you and 2) what type of error each test helps you avoid (i.e., false positive or false negative errors). Explain your reasoning. (2 marks for each) a. Plate the starting cells (untransformed cells – no plasmid added) on kanamycin-containing media. This will make sure the kanamycin concentrations are able to kill off the starting cells, because if there is an error the starting cells would live. This helps to avoid false positives. b. Plate a cell culture that you know is kanamycin resistant on kanamycin-containing media. This helps to avoid false negatives, because the conditions of the media could be contaminating to the E-coli for other reasons. Therefore, if the kanamycin-resistant cell culture also dies, we know there is still a possibility of the plasmid culture being resistant. c. Plate a cell culture that you know is kanamycin sensitive on kanamycin-containing media. This would help to avoid false positives- if the kanamycin sensitive culture were to live on the media it could indicate that the concentration of the kanamycin media is not enough. 2. How do each of the following traits aid the study of biology at a molecular level? (2 marks for each) 1 a. Low amount of repetitive DNA Low amounts of repetitive DNA can make the readings less complex, and allows for better focus on unique sequences and gene identification b. Diploid (not a trait of all model organisms) Is able to demonstrate genetic recombination and can offer unique mutations that haploid organisms may not be able to. c. Small, cheap to maintain - Science is expensive, and saving on costs here could provide more funding for other areas of your research. Small could indicate a lower genome size which would be easier to analyze Requires less space d. Transformable - Ability to implant foreign DNA, or “transgenes” Allows for genetic modifications for the improvement and further research of the cell Artificial recombination which provides new and unique genes sequences 3. List two drawbacks of focusing research on just a few model organisms. (2 marks) - Some of your findings could only apply to those select few organisms, and not be diverse across many species due to adaptation Studying model organisms could make it difficult to have new findings, given they are likely already well studied, as opposed to the less popular but more unknown species. 2
