Serial Dilutions Lab Report
1. Introduction: The goal of this lab was to demonstrate the microbiology technique of serial dilutions and how they can effectively be used in experiments. E. coli cells were exposed to UV light for various amounts of time in order to asses the effect on growth and thereby mutations since this cell was modified to not have photolyse no uvr genes for DNA repair and thus can only use the SOS response. Each group then diluted the cells accordingly based on their UV exposure time and counted the cells the next day. The counted colonies then allowed for back calculations to find the initial number of cells which then allowed for plotting of survival curves based on class data. E. coli cells were also investigated for the effect of cell number or concentration and beta-galactosidase induction. A culture of cells was grown over time
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One group did not list the identity of their bacteria and one group had listed invalided as their values, so those two groups data were thrown out. As seen above in the graph the positive control shows moderate beta-galactosidase activity and the negative control shows no activity as expected. Looking at the mutant, a large positive trend is seen in Miller Units overtime, more so than the positive control. Thus, the assumption can be confidently made the the mutant can in fact ferment lactose, which aligns with the MAC photos seen earlier. This also means that the mutation itself is likely not in the Lac-Z gene nor the promoter as both would prevent transcription and thereby production of beta-galactosidase. The gene that possess a mutation is likely a missense mutation in the Lac-Y gene or another gene that would still allow for transcription and thus production of beta-galactosidase as seen
One group did not list the identity of their bacteria and one group had listed invalided as their values, so those two groups data were thrown out. As seen above in the graph the positive control shows moderate beta-galactosidase activity and the negative control shows no activity as expected. Looking at the mutant, a large positive trend is seen in Miller Units overtime, more so than the positive control. Thus, the assumption can be confidently made the the mutant can in fact ferment lactose, which aligns with the MAC photos seen earlier. This also means that the mutation itself is likely not in the Lac-Z gene nor the promoter as both would prevent transcription and thereby production of beta-galactosidase. The gene that possess a mutation is likely a missense mutation in the Lac-Y gene or another gene that would still allow for transcription and thus production of beta-galactosidase as seen