3. Assume that in a bacterial species you discover a cluster ofthree genes (A, B, and C) that accountfor the enzymatic production of a cellulose-like carbohydrate (clc)that is needed as a component of its cell wall. When there issufficient clc is in the cell, the three enzymes are notsynthesized. However, when more clc is needed, the three enzymesare abundantly produced. This cluster of genes appears to be undercoordinate control because deletion of a distant gene (R)results in constitutive expression of all three genes even whenexcess clc is present. When mutations (P-) occur in a region upstream ofgene A, no synthesis of the three enzymes occurs even whenclc levels are extremely low. Mutations (O -)that occur right next to the P - mutationsresult in constitutive expression of all three genes even when clcis present at high levels.
(a) Do the three genes (A, B,and C) behave as if they were part of an operon?
(b) What type of control (positive or negative)seems likely to control the production of the three enzymes?
(c) What is the most likely function of theprotein produced from gene R?
(d) Do you expect that clc is an inducer,inhibitor, or corepressor?
(e) You discover that clc binds to the proteinmade from gene R. What is the most likely effect of this binding?(Hint: will it cause the R protein to bind DNA or fall off ofthe DNA?)
(f) Where do you think protein R binds?(Hint: P region or O region ?)
3. Assume that in a bacterial species you discover a cluster ofthree genes (A, B, and C) that accountfor the enzymatic production of a cellulose-like carbohydrate (clc)that is needed as a component of its cell wall. When there issufficient clc is in the cell, the three enzymes are notsynthesized. However, when more clc is needed, the three enzymesare abundantly produced. This cluster of genes appears to be undercoordinate control because deletion of a distant gene (R)results in constitutive expression of all three genes even whenexcess clc is present. When mutations (P-) occur in a region upstream ofgene A, no synthesis of the three enzymes occurs even whenclc levels are extremely low. Mutations (O -)that occur right next to the P - mutationsresult in constitutive expression of all three genes even when clcis present at high levels.
(a) Do the three genes (A, B,and C) behave as if they were part of an operon?
(b) What type of control (positive or negative)seems likely to control the production of the three enzymes?
(c) What is the most likely function of theprotein produced from gene R?
(d) Do you expect that clc is an inducer,inhibitor, or corepressor?
(e) You discover that clc binds to the proteinmade from gene R. What is the most likely effect of this binding?(Hint: will it cause the R protein to bind DNA or fall off ofthe DNA?)
(f) Where do you think protein R binds?(Hint: P region or O region ?)
