Insulin is a protein hormone that is critical for reducing the level of glucose

Question

Insulin is a protein hormone that is critical for reducing the level of glucose in the blood. Insulin is produced by beta-cells in the pancreas and the expression of the insulin gene is controlled by three regulatory transcription factors that are specific to the insulin gene. In addition, high levels of glucose in the blood increase the production of pre-mRNA molecules from the insulin gene.

a. Explain how the three regulatory transcription factors might be involved in regulating expression of the insulin gene only in pancreatic beta-cells. (1 point)

b. Do you expect that glucose is acting as an enhancer, a transcription factor, or an effector molecule in this gene regulation system? Explain your answer. (1 point)

3. In a healthy person, protein M is produced at moderate levels. But when a person has NON-M disease they produce lower levels of protein M. Is it the regulatory sequence or protein coding sequence of the gene that is most likely to be defective in this person? Explain your answer briefly. (1 point)

Explanation / Answer

a. the transcription factors are proteins that interact directly with regions of the DNA, normally the promoter of the gene, in this case the increase in levels of glucose, makes beta cells transport the glucose inside the cell through the GLUT-2 transporter, a chain reaction develops causing the three transcription factors enter the nucleus and the increase in the transcription of the insulin protein.

b. An enhaner is a sequence of the DNA that allows the increase of the transcription of the protein when the transcription factors are present. The transcription factors are proteins that can stick to specific regions of DNA. Glucose is not a DNA sequence nor a protein and can´t sense a specific sequence in the DNA, so glucose is more likely to be an effector molecule. This are molecules inside the cell that interact with proteins to increase a certain activity, in this case the production of insulin.

3.The regulatory sequence is more likely to be defective because there is still some level of protein M, if there was a defect on the sequence of the protein there would not be any protein at all because it would not transcribe or it would transcribe into a different protein, most likely not functional. The defect in the regulatory region can still allow the cell some production of the protein which sequence is intact.

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