Changes

:If the Cit+ change required a single mutation with a low but constant probability over time one would expect Cit+ mutations to be distributed across cells taken from any generation of the experiment. On the other hand, if a 'potentiating' mutation had to arise at some point in the cultures before the final Cit+ mutation could function, then one would expect the probability for Cit- cells to mutate to Cit+ cells would increase with samples of cells taken from later cultures.

:If the Cit+ change required a single mutation with a low but constant probability over time one would expect Cit+ mutations to be distributed across cells taken from any generation of the experiment. On the other hand, if a 'potentiating' mutation had to arise at some point in the cultures before the final Cit+ mutation could function, then one would expect the probability for Cit- cells to mutate to Cit+ cells would increase with samples of cells taken from later cultures.

:Blount ran the experiment and found that Cit+ mutants arose more frequently in cells taken from later generations in the culture. The Monte Carlo tests were used to assess how likely the pattern of results would fit the models. The statistical significance (smaller P-values mean greater significance), was calculated for each experiment and the combination of experiments. The numbers suggest the distribution of mutants was not randomly distributed across the experimental generations, they tended to appear in cells taken from the later generations. This would argue against the single-mutation, constant, low-probability hypothesis. It appears that a pre-adaptive mutation had to have arisen first, followed by the mutation the finally allowed the cells to utilized citrate. Future work in Lenski's lab will focus on trying to identify the various mutations involved. I hope that helps.--[[User:Argon|Argon]] 20:25, 15 July 2008 (EDT)

:Blount ran the experiment and found that Cit+ mutants arose more frequently in cells taken from later generations in the culture. The Monte Carlo resampling tests were used to assess how likely the pattern of results would fit the models. The statistical significance (smaller P-values mean greater significance), was calculated for each experiment and the combination of experiments. The numbers suggest the distribution of mutants was not randomly distributed across the experimental generations, they tended to appear in cells taken from the later generations. This would argue against the single-mutation, constant, low-probability hypothesis. It appears that a pre-adaptive mutation had to have arisen first, followed by the mutation the finally allowed the cells to utilized citrate. Future work in Lenski's lab will focus on trying to identify the various mutations involved. I hope this brief explanation helps.--[[User:Argon|Argon]] 20:25, 15 July 2008 (EDT)