Question

Which enzyme/s will be produced in a cell in which there is a non-sense mutation in the lac y gene?

• A. Lactose permease
• B. Transacetylase
• C. Lactose permease and transacetylase
• D. β-galactosidase

Answer 1

The correct option is D β-galactosidase

An operon is a coordinated group of genes that act as a single regulatory unit.

The lac operon has three structural genes (lac z, lac y and lac a), an operator region (o), promoter region (p) and regulatory gene (i).


z gene codes for β-galactosidase – responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose.

y gene codes for permease - increases permeability of lactose.

a gene codes for transacetylase - plays an important role in lactose utilization.

A type of mutation in which the resulting codon is a stop codon is called nonsense mutation and hence transcription stops from that point.


So, the correct answer is option A.