Chapter 12.4, Problem 6MI

Summary Introduction

To determine:

The features of Trp and Lac operon.

Introduction:

Operon is a unit of DNA, which is a cluster of genes which have a single promoter. They are expressed together or not all expressed.

Explanation of Solution

Tryptophan operon or trp operon is a segment of the genes, which encodes for the enzyme responsible for production of tryptophan in the cell. In the abundance of tryptophan, the repressor of trp gene binds to the promoter which stops enzyme production activity.

The lac operon is an operon which is activated in the presence of lactose molecules. The binding of allolactose causes the expression of lac operon and metabolism of the lactose.

The features of trp and lac operon are given as follows:

	Trp Operon	Lac operon
Respond to the presence of	Tryptophan	Lactose
Transcription is turned on when	Tryptophan level is low	Allolactose bind to operator
The repressor is active when	Tryptophan is abundant	No lactose
When operon is turned on cell can	Produce the enzymes for synthesis of tryptophan	Synthesise enzyme for lactose digestion.