Match List-I with List-II
| List-I | List-II |
|---|---|
| Name of the gene | Encodes |
| (A) ‘i’ | (I) Permease |
| (B) ‘z’ | (II) Repressor |
| (C) ‘y’ | (III) Transacetylase |
| (D) ‘a’ | (IV) β- Galactosidase |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) - (II), (B) - (IV), (C) - (I), (D) - (III)
(A) ‘i’ — this matches (II) Repressor. The i gene is the regulator gene of the lac operon. Its repressor protein binds the operator and keeps the operon switched off when lactose is absent.
(B) ‘z’ — this matches (IV) β- Galactosidase. This enzyme breaks lactose into galactose and glucose.
(C) ‘y’ — this matches (I) Permease. Permease makes the cell membrane permeable to lactose, so lactose can enter the cell.
(D) ‘a’ — this matches (III) Transacetylase. The third structural gene codes for transacetylase.
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.”