The efficiency of the promoter for the repressor protein and whether the synthesis of the repressor is constitutive or inducible. Introduction: The regulatory proteins bind to the DNA (deoxyribonucleic acid) and play a key role in determining which genes are to be activated. These are of two types, namely, the repressor and activator proteins. The proteins, whose synthesis is regulated by inducers are known as inducible proteins, while the proteins that are synthesized at a constant rate all the time are known as constitutive proteins. In the given case, a regulatory gene codes for the repressor protein, which is synthesized in small quantities at a constant rate. This protein acts on the lac operon of Escherichia coli ( E. coli ). A promoter is a DNA region, which initiates the process of transcription of a certain gene by binding with the ribonucleic acid (RNA) polymerase.

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Chapter 16.1, Problem 4R

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The efficiency of the promoter for the repressor protein and whether the synthesis of the repressor is constitutive or inducible.

Introduction:

The regulatory proteins bind to the DNA (deoxyribonucleic acid) and play a key role in determining which genes are to be activated. These are of two types, namely, the repressor and activator proteins. The proteins, whose synthesis is regulated by inducers are known as inducible proteins, while the proteins that are synthesized at a constant rate all the time are known as constitutive proteins.

In the given case, a regulatory gene codes for the repressor protein, which is synthesized in small quantities at a constant rate. This protein acts on the lac operon of Escherichia coli (E. coli). A promoter is a DNA region, which initiates the process of transcription of a certain gene by binding with the ribonucleic acid (RNA) polymerase.

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The lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) I+ OC Z+ I+ O+ Z+ (Lactose present) I- O+ Z+

The lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) IS O+ Z+ IS OC Z+

In the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answer