A synthetic repressor binds a single operator inserted into the Escherichia coli…
PHYSICS · Multi-part · Fermi University Physics · Biophysics & Medical Physics · Genetic circuits, regulation and biological information · Genetic circuits, regulation and biological information
Forces, Machines and Signals, Ch Genetic circuits and biological pattern
Problem
A synthetic repressor binds a single operator inserted into the Escherichia coli chromosome, which offers NNS=4.6×106 non-specific sites. Each repressor tetramer has two DNA-binding heads, the operator's binding energy relative to non-specific DNA is Δε=−13.0kBT, and there are R=20 tetramers per cell.
((a)) Using the promoter thermodynamic model, calculate the fold change in expression of the gene controlled by this operator.
((b)) State the repression factor, the reciprocal of the fold change.
((c)) How many tetramers would this operator need for twentyfold repression, a fold change of 0.05?