Question

You infect cells with Phage T4 and add 14C radioisotope at various times after infection to radiolabel phage proteins. You make lysates of cells at various time points after infection and run them on a polyacrylamide gel and subsequently blot the proteins onto a filter to expose to film. You get the banding pattern shown in panel A. You repeat the same experiment but this time you mutagenize the virus prior to infecting the cells and you get the bands shown in panel B. Panel A Minutes Panel B Minutes 0-5 Х 5-10 10-20 >30 0-5 5-10 10-20 >30 Z Regarding the experiment above, which of the following statements is most likely correct? Protein Y is not essential Protein X is a non-essential gene Protein Y was regulated by protein X Protein X is likely a regulatory protein affecting expression of protein Z

Answer 1

Correct answer: c, Protein Y was regulated by protein X. Initially before introducing the mutation in the virus from the results in Panel A it can be observed that Protein X and Z are expressed in the initial time period i. e. from 0 to 10 minutes. As the minutes goes on increasing, the expression of Protein X and Z decreases. With the downregulation of protein X after 10 minutes of treatment, the expression of protein Y is upregulated as seen in the result of Panel A after 10-30 minutes of the treatment. The expression of Protein X is very low or inhibited after 10-30 minutes. After introducing mutation in the virus, the expression of Protein X can be seen in the Panel B but there is no expression of Protein Y seen. This means that the expression of Protein Y was regulated by Protein X.