Question

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

• A. $\beta$-galactosidase
• B. Lactose permease
• C. Transacetylase
• D. Lactose permease and transacetylase

Answer 1

The correct option is A $\beta$-galactosidase


The lac operon of E. coli has three structural genes.
Z secretes $\to$ $\beta$-galactosidase
Y secretes $\to$ Permease
A secretes $\to$ Transacetylase
If there is a nonsense mutation in the y gene of the lac operon, then the genes encoding permease and transacetylase are not translated. Since only the lac Z gene is encoded, there is an accumulation of $\beta$-galactosidase in the cell.