As you study the lambda repressor operators, you decide to test whether one oper

Question

As you study the lambda repressor operators, you decide to test whether one operator binds to the repressor protein with higher affinity than the other. You design an experiment where you will set up multiple protein-DNA binding reactions, each with the same concentration of operator DNA but with a variable concentration of lambda repressor protein. After you perform eleven such experiments at different protein concentrations, you analyze your results by running them out on a gel (an assay called "EMSA" or a mobility shift assay). The horizontal line above the gel indicates a constant concentration of the operator DNA in each reaction; the black triangle indicates an increasing concentration of the repressor protein in the reactions towards the right. You now compare the binding affinities for the lambda repressor for OR1 and OR2. You do this by repeating the same DNA-binding experiment, although this time you use OR2 rather than OR1. Your data is shown below. Which operator site binds the repressor with a greater affinity and how do you know? It turns out that you cannot attribute all of the regulation of this operon to just this small region of the DNA alone. Using random mutagenesis, you discover that a segment of DNA on the other end of the chromosome seems to also be involved with regulating the lambda repressor. Briefly explain how this could be.

Explanation / Answer

d) As the bound form is more with OR1 there are chances that repressor can bind to this DNA more tightly. than OR2. where bound form is less.

e) The sites for binding of lamda repressor are present on the other end of chromosome.

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