Question

In $lac$ operon genes $a,i,y$ and $z$ code for

• A. Repressor protein, permease, ꞵ-galactosidase, transacetylase
• B. Transacetylase, permease, ꞵ-galactosidase, repressor protein
  
• C. Transacetylase, repressor protein, permease, ꞵ-galactosidase
• D. Permease , transacetylase, repressor protein, ꞵ-galactosidase

Answer 1

The correct option is C Transacetylase, repressor protein, permease, ꞵ-galactosidase

The $lac$ operon
The $lac$ operon is an inducible operon system that remains usually in a repressed condition and gets activated only when the substance to be metabolised (lactose) is present.
Elements of lac operon
The lac operon consists of the control elements and three structural genes
$\bullet$lac z: It codes for β-galactosidase enzyme which hydrolyses lactose into glucose and galactose.
$\bullet$lac y: It codes for permease enzyme which increases the permeability of the cell to β-galactosides.
$\bullet$lac a: It codes for the transacetylase enzyme which transfers acetyl group to β-galactosides etc.
$\bullet$lac i: It codes for repressor protein. This binds to the operator region of the DNA and stop the transcription of structural genes.
Final answer
(B) Transacetylase, repressor protein, permease, ꞵ-galactosidase