Chapter 14, Problem 23P

Summary Introduction

To analyze:

An inducible operon of bacteria has three genes R, T, and S – same as lactose operon. These genes play a role in the regulation of transcription. These genes can be operator gene, regulatory gene, and structural gene (codes for structural enzyme). In the question, a table is provided in which $\text{"+"}$ represents that the synthesis of structural enzyme is active and $\text{"-"}$ represents no synthesis of structural enzyme. By using the given information, the question asked to determine from given genotype which gene is operator gene, which one is regulatory gene, and which one is structural gene.

Introduction:

A unit of DNA that has a group of genes controlled by a single promoter is termed as an operon. The operon possesses different regions (operator, promoter and structural genes); each region has a different role. Operator region is a short region of operon that controls transcription of genes by interacting with regulatory proteins. Regulatory proteins include proteins that act as transcription factor and facilitate the synthesis of protein in bacteria. Any protein which has its impact on the region of operon (DNA), which is transcribed in the transcription, is a regulatory protein.

The gene which codes for the protein other than the regulatory protein is termed as the structural gene. The product of structural genes is structural protein and enzymes.