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Submitted by cgualtieri on Wed, 12/12/2018 - 16:23

The results from this experiment were not fully in accordance with my expected results. The tubes containing glucose and sucrose turned yellow after incubation, and a bubble of CO2 gas was present in the Durham tube. These results were expected, and showed that S. cerevisiae was able to ferment these two sugars and produces CO2 gas in the process. However, the tube containing lactose was also yellow and contained a bubble in the Durham tube after incubation, which was not expected. This shows that S. cerevisiae is able to ferment lactose along with glucose and sucrose. I did not expect to see this result because lactose is not present in the natural environment of S. cerevisiae. This result could be explained by a gain-of-function mutation in the strain of S. cerevisiae used in this experiment. Another explanation could be that the pH sensitive dye used was too sensitive and turned yellow with only a very small change in the solutions pH.



Rather than saying your experiment "shows" something, I would suggest that you say it "suggests." As scientists we are not really proving anything, rather we are gathering evidence. So you cannot be certain that these organisms are able to ferment sugar, rather you have further evidence which suggests the ability to ferment.