Consider a genetic network consisting of gene A whose product activates the transcription of gene R. Imagine that the concentration of protein A is suddenly changed by a significant amount. The following graphs show how the concentration of protein R would then change over time to reach steady state again. The two curves (1 and 2) in each graph correspond to systems that have different transcription rates for A. For one of the two graphs (A or B) a negative feedback loop is present, in which protein R represses the transcription of gene A. Which conclusion is correct according to these results?
A) The negative feedback loop makes the system slower in reaching the steady state.
B) With negative feedback, the steady-state concentration is less sensitive to fluctuations in kinetic rate constants.
C) Higher transcription rates for gene A result in lower steady-state levels of protein R both with and without negative feedback.
D) All of the above.

Question

Consider a genetic network consisting of gene A whose product activates the transcription of gene R. Imagine that the concentration of protein A is suddenly changed by a significant amount. The following graphs show how the concentration of protein R would then change over time to reach steady state again. The two curves (1 and 2) in each graph correspond to systems that have different transcription rates for A. For one of the two graphs (A or B) a negative feedback loop is present, in which protein R represses the transcription of gene A. Which conclusion is correct according to these results? 
A) The negative feedback loop makes the system slower in reaching the steady state. 
B) With negative feedback, the steady-state concentration is less sensitive to fluctuations in kinetic rate constants. 
C) Higher transcription rates for gene A result in lower steady-state levels of protein R both with and without negative feedback. 
D) All of the above.

Quizplus · Accepted Answer

Negative feedback can protect the cell from perturbations that continually arise in its environment. Such perturbations can change the kinetic parameters. With negative feedback, the steady-state concentration in a system changes to a lesser extent upon fluctuations in these parameters. Please refer to Figure 8-77.

Consider a Genetic Network Consisting of Gene a Whose Product