Lac Operon System: Overview

The lac operon system is a genetic regulatory system found in bacteria, specifically in Escherichia coli (E. coli). It consists of a group of genes that are involved in the metabolism of lactose, a sugar present in the environment. The lac operon is responsible for the regulation of these genes based on the availability of lactose.

Components of the Lac Operon

1. Promoter: The promoter is a DNA sequence located upstream of the lac operon genes. It serves as the binding site for RNA polymerase, which initiates transcription.

2. Operator: The operator is another DNA sequence located between the promoter and the first gene of the lac operon. It acts as a regulatory switch, controlling the transcription of the genes downstream.

3. Structural Genes: The lac operon contains three structural genes: lacZ, lacY, and lacA. These genes are responsible for the production of enzymes involved in lactose metabolism.

Identification of the Gene Coding for β-galactosidase

β-galactosidase is an enzyme involved in the breakdown of lactose into glucose and galactose. It is coded by the lacZ gene within the lac operon.

The lacZ gene is responsible for the production of β-galactosidase, which hydrolyzes lactose into its component sugars. This gene plays a crucial role in the metabolism of lactose.

Identifying the Correct Gene

In the given options, option 'C' is the correct answer, representing the lacZ gene. This gene codes for β-galactosidase, the enzyme responsible for lactose metabolism.

The other options, option 'A' (y-gene), option 'B' (I-gene), and option 'D' (a-gene), are not associated with the lac operon system and do not code for β-galactosidase.

In conclusion, the lac operon system consists of several genes involved in lactose metabolism. The lacZ gene codes for β-galactosidase, an enzyme responsible for the breakdown of lactose. Therefore, option 'C' is the correct answer.