This lesson is part of a sophomore level biochemistry course to introduce the concepts of experimental design. Students are provided with the description of an experiment designed to examine the effect of an electric field on bacterial growth. They are given initial observations from the experiment (inhibition of growth and an elongation phenotype for the bacteria) and asked to consider control experiments to evaluate whether the electric field is directly responsible for the effect. Students are prompted with questions then work in groups and share ideas. Ultimately it is revealed that platinum in the wires reacts to form cisplatin compounds that prevent cell division. Next the instructor explains that ciplatin reacts covalently with DNA and causes a bend or kink at the site of attachment. This led to the isolation of proteins that preferentially bind cisplatin modified DNA. Quantitative analysis of DNA-protein binding is presented to evaluate the affinity of proteins for unmodified and ciplatin modified DNA. Students are provided data from multiple binding trials and asked to evaluate the data. Students discuss and share ideas in class. Averages and standard deviations are discussed and calculated. Finally, data is presented from published studies that include averages and standard deviations. The lesson is designed to reinforce the concepts of control groups, quantitative analysis, statistical variation and display of data.
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