The hypothetical BSc operon of bacteria encodes the HD enzyme and the P enzyme.
ID: 91313 • Letter: T
Question
The hypothetical BSc operon of bacteria encodes the HD enzyme and the P enzyme. Expression of this operon is regulated in response to substance X and substance Y. Five different mutants have been isolated that show abnormal regulation of expression of the BSc operon. The table below shows the level of enzyme activity for these different mutants. First the bacterial cells were incubated in minimum medium, then compound 1 was added, and then compound 2 was added after further incubation: a) Which observations indicate that the BSc operon is inducible? b) Which observations indicate that the BSc operon is also repressive? c) Which mutant show's gene expression consistent with being a loss - of - function mutation in: i. the promoter of this operon ii. the DNA sequence bound by the positive regulator iii. the DNA sequence bound by the negative regulator iv. the gene encoding HD enzyme v. the gene encoding P enzyme d) Predict the enzyme activity (using the same format as the table above) that would result from a loss - of - function mutation in: i. the gene encoding the positive regulator ii. the gene encoding the negative regulator iii. both (i) and (ii), i.e. a double mutantExplanation / Answer
Answer:
1) which observations indicate that the BSC operon is inducible?
Answer: Since wild type cells have high enzyme activity after the addition of substance X therefore it indicates that the BSc operon is inducible.
2) Which observation indicate that BSc operon is also repressible?
Answer: Since addition of substance X decreases the enzyme activity of the wild type cells, therefore this observation indicates that BSC operon is also repressible.
3) Which mutant shows gene expression consistent with being a loss of function mutation in:
1) the promoter of this operon - mutant 5 (since mutant 5 cells expression levels are low in all conditions)
2) the DNA sequence bound by the positive regulator
3) The DNA sequence bound by the negative regulator
4) the gene encoding HD enzyme - mutant 1
5) the gene encoding P enzyme - mutant 3
*Working on all parts, will update soon.
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