Question

6. The gene for a hormone necessary for insect development contains binding sites for three transcription regulators called A, B, and C. Because the binding sites for A and B overlap, A and B cannot bind simultaneously. You make mutations in the binding sites for each of the proteins and measure hormone production in cells that contain equal amounts of the A, B, and C proteins. Figure 08-65 summarizes your results. For each of the following sentences, indicate if the statement is true or false and explain your reasoning AO DA transcription start site Binding site Hormone production OH A.B.C+ Off A-B.CH A+B-C+ Off A+B+C- Low level A-B-C Off A+ B-C- Low level High level A-B-C- - indicates a mutant site A-BC- Off A. B. Figure Q8-65 Protein A and B are transcription activators. True/False: How do you know? Protein C is a transcription repressor. True/False: How do you know 2: Protein A is able to activate transcription more than Protein B. True/False: How do you know 2: C.

Answer 1

A. False.

Protein B is a transcriptional activator but not A. Binding of A doesn't increase the level of transcription in any cases. Low levels of hormone is produced due to the normal transcription that is happening in the absence of a repressor. Transcription activators are supposed to increase the amount of transcription to produce high levels of product.

B. True.

Protein C is a transcriptional repressor. When Protein C binds to it's site , transcription is halted leading to no production of the product.

C. False.

Protein B is able to activate transcription more than Protein A. Here we can see that whenever just Protein A binds without repressor it leads to low level of hormone production. Same goes when both A and B binds together. When Protein B binds alone , it leads to high level of hormone production indicating than actually Protein B is the transcriptional activator.