A) Based on your knowledge of how the lac operon works and the mutations caused

Question

A) Based on your knowledge of how the lac operon works and the mutations caused by chemicals in the water, which mutation type(s) do you expect to find in the cells?

B) From Part A, explain how this type of mutation(s) in E.Coli in gut flora can lead to symptoms of weakness, lethargy, and even death, that the scientists observed

2) The scientist team notices that the pups who are still nursing from their mothers are especially weak and suffer from high death rates. Following the logic of your answer to the previous question, explain why nursing pups are especially affected and weakened by the presence of the chemicals in the water.

3) In the lab, the experts notice that some E. coli cells are able to normally express the lac operon, even in the presence of glucose. This leads the team to hypothesize that not all E. coli cells have the same mutation. Based on your knowledge of the mutations types, which mutation (s) do you expect to find in these particular cells?

A population of sea lion has been found in polluted waters in the Atlantic Ocean. The sea lions, especially the pups, are weak, emaciated, lethargic, and have very little energy Usually, normal sea lions have gut flora in the intestines consisting of populations of bacteria, including E. coli, which help digestion and break down food into energy. Gut flora is very important to for sea lion health. The scientist teams finds chemicals in the water, which cause mutations impacting the lac operon of E. coli the in the gut flora of the sea lions, affecting the lac operon's ability to function normally. Use the figure below depicting a wild type operon (a) and examples of mutation (b-d) to answer the following questions. (c) I (repressor mutation) (a) / (wild type) Repressor binds operator when the inducer is absent and forms an inducer- repressor complex when inducer is present Repressor protein mutation prevents repressor binding to the operator and produces constitutive synthesis of the lac operon lac repressor protein Allolactose Mutant protein (d) (super-repressor mutation) (b) Of (operator constitutive mutation) Operator-site mutation prevents repressor protein binding and leads to constitutive synthesis of the lac operon. Repressor protein mutation blocks binding to the inducer, preventing formation of the inducer-repressorcomplex. Mutant repressor protein binds to the operator, preventing transcription. lac repressor protein Super-repressor mutant

Explanation / Answer

A) The chemical present in water might be causing mutation of type D,where due to muatation in the inducer binding site of repressor occurs which is called superrepressor , superepressor is unable to bind inducer , Thus it will remain bound to the operator and prevent binding of RNA polymerase onto the lac promoter thereby preventing transcription. Thus lactose metabolising genes will not be synthesized even in presence of lactose thus gut flora resident bacterial is uable to utilise lactose.

In case B and C due to consititutive expression of lac genes even in absence of lactose will lead to transcription of the genes all the time, Therefore metabolic energy will be wasted and the seals will feel letahrgic and remain deprived.

B) This happens because they require glucose all the time as the energy source, if the glucose is limiting they bacteria generally utilises lactose and fulfills metabolic needs. But due to the mutation given in

Case 2 and 3 because of constitutive expression of lac genes even in absence of lactose , will be a metabolic burden to the cell and lead to wastage of cellular energy and therfore the seals will feel letahrgic and can die.Case 4 , they are unable to shut on the trasncription of lactose utilising genes and hence cannot utilise lactose. The energy demands will not met and therefore the sea lion pups feel lethargic and it can lead to death also.

2) Since the pups are nurtured by their mother and their gut microbiome is still not developed yet, the gut microbial diversity is not rich in pups they derive energy from their mother only. Mother milk contain lactose which needs to be metabolised , That rquires lac gene transcription, If it remain on all the time(constitutive as in caseb and c) then also metabolic energy will be wasted.

Case 4 They will die because lac operon will remain shut off and they cannot utilise lactose present in mothers milk, it will be even more fatal.

3)In those bacteria which are normally expression lac operon even in presence of glucose will have mutation in CAP protein which cannot responds to the levels of cAMP and glucose, and continue transcribing lac genes.

Since high glucose- low cAMP--- less cAMP-CAP Complex---- cannot bind to DNA efficiently---- RNA POL weakly binds to Lac genes---- Transcription low.

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