Question

Identify the incorrect statement from the following with reference to lac operon.

• A. It is a unit of gene expression and regulation for lactose sugar metabolism in E. Coli.
• B. Lactose sugar enters the cell due to the activity of enzyme permease.
• C. Operators are present between promoters and structural genes.
• D. The structural gene 'z' codes for $\beta$ -galactosidase, 'y' for transacetylase and 'a' for permease.

Answer 1

The correct option is D The structural gene 'z' codes for $\beta$ -galactosidase, 'y' for transacetylase and 'a' for permease.

Lac operon is an operon which is involved in the regulation of lactose metabolism in several enteric bacteria including Escherichia coli. It is an inducible operon. It contains promotor, operator, three structural genes and terminator. the three structural genes are namely, lacZ, lacY and lacA. LacZ gene encodes for β-galactosidase, lacY encodes for β-galactoside permease and lacA encodes for β-galactoside transacetylase. A β-galactosidase cleaves galactose into glucose and galactose. Permease helps in transport of lactose sugar into the cell. Transacetylase helps in transfer of an acetyl group from acetyl-CoA to β-galactosides.

Thus, the correct answer is option D.