Question

Choose the correct answer from the alternatives given :
The given figure shows lac operon and its functioning. Select the option which correctly labels A, B, X, Y and Z.

• A. A - Repressor, B - Inducer, X - $\beta$ galactosidase, Y - Permease, Z - Transacetylase
• B. A - Repressor, B - Inducer, X - Permease, Y - $\beta$ galactosidase , Z - Transacetylase
• C. A - Inducer, B - Repressor, X - $\beta$ galactosidase , Y - Permease, Z - Transacetylase
• D. A - Inducer, B - Repressor, X - $\beta$ galactosidase, Y - Transacetylase, Z - Permease

Answer 1

The correct option is A A - Repressor, B - Inducer, X - $\beta$ galactosidase, Y - Permease, Z - Transacetylase

The Lactose operon gene in E.coli is a polycistronic gene, A is a repressor that binds to the inducer region in absence of Lactose, in presence of Lactose the inducer protein binds to the repressor.

X- is $\beta$ Galactosidase that converts lactose to glucose and galactose.

Y-permease, a transporter protein that transports Lactose from the medium into the cell

Z- is transacetylase that transfers acetyl group from acetyl CoA to $\beta$ galactosides

So, the correct answer is 'A Repressor, B Inducer, X -

ββ galactosidase, Y Permease, Z - Transacetylase'