Match List-I with List-II
| List-I Genes of lac Operon | List-II Codes for |
|---|---|
| (A) i | (I) β-galactosidase |
| (B) z | (II) Transacetylase |
| (C) a | (III) Permease |
| (D) y | (IV) Repressor |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A)-(IV), (B)-(I), (C)-(II), (D)-(III)
(A) i — this matches (IV) Repressor. The i gene is the regulator gene; “i” comes from inhibitor. Its repressor protein binds to the operator and stops transcription when lactose is absent.
(B) z — this matches (I) β-galactosidase. This enzyme hydrolyses lactose into galactose and glucose, which the cell can use.
(C) a — this matches (II) Transacetylase. The a gene is the third structural gene of the lac operon, and it codes for transacetylase.
(D) y — this matches (III) Permease. Permease increases the permeability of the cell to lactose, so that lactose can enter the cell.
Note: A similar question was also asked in CUET (UG) 2024 on 29-05-2024 (Slot 1), and in CUET (UG) 2022 on 30-08-2022 (Slot 2).
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.”