Problem Set 3A Phage genetics 1. Five mutants a-e in phage π are temperature sensitive for growth. All the mutants grow normally (i.e. make plaques) at 30° but do not grow at all at 40°. As your ﬁrst step in characterizing these mutants you perform double infections of the host E. coli strain at 30°. You allow the doubly infected bacteria to lyse then titrate the phage by plating on E. coli at 40°. You obtain the following data (the number is the burst size for each infection). a b c d e WT a0 900 850 105 b00 100 100 95 c000 100 d0 85 98 e0 110 In a second experiment you perform double infections as before, but then separately titrate the resultant bursts at 30° and at 40°. Below are your data, plotted as the ratio (burst size at 40°/burst size at 30°). a b c d e a0 0.0030 0.009 0.001 b 10
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