Use the information in the gene circuit here to answer the following questions b
ID: 210675 • Letter: U
Question
Use the information in the gene circuit here to answer the following questions bacterlum 1. When you add a small amount of the signal peptide to a flask containing a population of E. Luminescent, what will be the result? Discuss the levels of GB protein, signal peptide, and the status of the transcription factors in your answer Pdding a omall amount of the molecule will reduce +he amon+-op Sigral pepide erepressor ai no ard to He operator Concentration of External Signal Molecule 2. Explain the levels of transcription for both genes (GB and signal peptide) when there is no signal peptide present. Use terms such as repressor and activator in your answer 3. Predict the phenotype for the bacterium containing a mutated repressor such that it could no longer bind to the DNA. Predict the phenotype for the bacterium containing a mutated activator such that it could no longer bind to the GB protein. 4.Explanation / Answer
1- Signal peptide binds to the repressor which leads to the production of GB protein. This GB protein then, in turn, binds to the activator of a signal peptide and this leads to the production of more signal peptide. This is called as the positive feedback loop
In the given case there will be more production of GB protein and signal peptide and transcription factor for GB protein can no longer bind to the GB protein gene and transcription factor of Signal peptide can bind to its gene.
2- When there is no signal peptide the levels of GB protein and signal peptide is very very less or they are not at all present in the cell.
When the signal peptide is not present repressor for GB protein is bound to its gene. Since there is no GB protein so activator of signal peptide can no longer bind to site on signal peptide gene.
3- When the repressor is mutated in such a way that it can no longer bind to its site on GB protein gene, in that case, there will be a constitutive expression of GB protein and in turn, constitutive expression of signal peptide and bacteria will show luminescence
4- In that case, there will be the production of GB protein but there will not be any production of the signal peptide. So bacteria will not show any luminescence.
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