PART IV: MAJOR QUESTIONS (20 points each) 1: Please describe how an mRNA gene is transcribed, processed and translated in human cells. What are the possible mechanisms in regulating the expression of this gene 2 (20 points): A bacterium is found to metabolize a rare sugar produced by a plant that the bacteria grow on. However, the bacteria prefer glucose as the energy source. The problem is, if you want to finish this course with a sat isfied score, you must figure out the regulatory mechanism that the bacteria used to determine the sugar choice The gene involving in the rare sugar metabolism has been identified as fin3. You can use northern blot to analyze the expression of fun3 and use dNA footprinting to analyze the binding of proteins to the control elements of fiun3 gene. The following table shows the experimental results Glucose Rare sugar Levels of Binding of proteins presence presence fun3 RNA Protein a binds to the promoter region Protein C binds upstream of the promoter Protein a binds to the promoter region ++ Protein b binds to the promoter region Protein C binds upstream of the promoter Protein b binds to the promoter region 1. Please propose a mechanism to explain the above results. You should focus on the question"How does the expression of fin3 gene is tightly regulated so that it is only highly expressed when the rare sugar is the only carbon source". You must answer what proteins A, B and C are (8 points) 2. How is protein A regulated? (2 points) (1) glucose turns the repressor on (4)the rare sugar turns the repressor off 3. How is protein C regulated? (1)glucose turns the activator on (2)glucose turns the activator off (3)the rare sugar turns the activator on (4)the rare sugar turns the activator off 4. How could you make the bacteria always use the rare sugar as the energy source even in the presence of glucose?( 8 points)PART IV: MAJOR QUESTIONS (20 points each) 1: Please describe how an mRNA gene is transcribed, processed and translated in human cells. What are the possible mechanisms in regulating the expression of this gene? 2 (20 points): A bacterium is found to metabolize a rare sugar produced by a plant that the bacteria grow on. However, the bacteria prefer glucose as the energy source. The problem is, if you want to finish this course with a satisfied score, you must figure out the regulatory mechanism that the bacteria used to determine the sugar choice. The gene involving in the rare sugar metabolism has been identified as fun3. You can use northern blot to analyze the expression of fun3 and use DNA footprinting to analyze the binding of proteins to the control elements of fun3 gene. The following table shows the experimental results Glucose presence Rare sugar presence Levels of fun3 RNA Binding of proteins - - - Protein A binds to the promoter region Protein C binds upstream of the promoter + - - Protein A binds to the promoter region - + +++ Protein B binds to the promoter region Protein C binds upstream of the promoter + + + Protein B binds to the promoter region Questions: 1. Please propose a mechanism to explain the above results. You should focus on the question “How does the expression of fun3 gene is tightly regulated so that it is only highly expressed when the rare sugar is the only carbon source”. You must answer what proteins A, B and C are. (8 points) 2. How is protein A regulated? (2 points) (1) glucose turns the repressor on (2) glucose turns the repressor off (3) the rare sugar turns the repressor on (4) the rare sugar turns the repressor off 3. How is protein C regulated? (2 points) (1) glucose turns the activator on (2) glucose turns the activator off (3) the rare sugar turns the activator on (4) the rare sugar turns the activator off 4. How could you make the bacteria always use the rare sugar as the energy source even in the presence of glucose? (8 points)