The hypothetical fox operon includes the sequences: foxA, foxB, foxC and foxD. T
ID: 272893 • Letter: T
Question
The hypothetical fox operon includes the sequences: foxA, foxB, foxC and foxD. These sequences may represent either structural genes or regulatory sequences. Regulation of expression of the fox operon depends on the compound Fox. The fox operon encodes enzyme 1 and enzyme 2. Levels of activity of these enzymes were measured in a wildtype and mutant strains, as shown in the table (all are loss-of-function mutants) Fox compound absent Fox compound present Enzyme 1 activity zero zero zero zero high Enzyme 2 activity zero zero zero zero high Enzyme 1 activity Enzyme 2 activity high high zero zero high Genotype wildtype foxA foxB foxC foxD Is the fox operon inducible or repressible? Explain your answer Which sequence from foxA, foxB, foxC and foxD is the zero zero a) b) Structural gene or enzyme1 Structural gene or enzyme 2 Promoter Operator c) Is regulation of the fox operon via a positive or negative mechanism? Explain your answer d) (You need to use your answer to (c) to answer this part.) If the protein that binds the operator is encoded by the foxR gene, complete another row to the table above for a foxR loss-of-function mutant.Explanation / Answer
1) when fox compound is present it induces the expression of enzyme 1 and 2. so it is an inducible operon.
2) foxA = structural gene for enzyme 1.
foxB = Promoter.
fox C = structural gene for enzyme 2.
foxD = operator.
3) when fox is present it will bind to the fox repressor protein and inactivates it so it will not bind to the operator sequence. so it is a positive mechanism.
4) if fox R encodes repressor protein then its presence will affect the enzyme 1 and 2 production. when fox compound is absent then it will bind to the operator and no expression of enzyme1 and 2 will observe. In case of fox compound is present, repressor will bind to compound so it will not be able to bind to operator and structural enzyme 1 and 2 will produce.
in case of loss of function mutation in foxR results in high production of enzyme 1 and 2 in both conditions i.e. presence and absence of fox compound.
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