Match List I with List II
| LIST I (Genes in lac operon) | LIST II (Products coded for) |
|---|---|
| A. i-gene | I. β-galactosidase |
| B. z-gene | II. Transacetylase |
| C. y-gene | III. Repressor protein |
| D. a-gene | IV. Permease |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-I, C-IV, D-II
(A) i-gene — this matches (III) Repressor protein. The i gene is the regulatory gene of the lac operon. Its repressor binds the operator and switches the operon off when lactose is absent.
(B) z-gene — this matches (I) β-galactosidase. This enzyme breaks lactose into glucose and galactose.
(C) y-gene — this matches (IV) Permease. Permease makes the cell let lactose in.
(D) a-gene — this matches (II) Transacetylase. The a gene codes for transacetylase, the third enzyme of the operon.
Note: A similar question was also asked in CUET (UG) 2025 on 29-05-2025 (Slot 1), and in CUET (UG) 2024 on 29-05-2024 (Slot 1).
NCERT Extract:
The Lac Operon – “… The lac operon consists of one regulatory gene (the i gene – here the term i does not refer to inducer, rather it is derived from the word inhibitor) and three structural genes (z, y, and a). The i gene codes for the repressor of the lac operon. The z gene codes for beta-galactosidase (β-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose. The y gene codes for permease, which increases permeability of the cell to β-galactosides. The a gene encodes a transacetylase.”