Match the 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) B- 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)
| List-I | List-II |
| Name of the gene | Encodes |
| (A) 'i' | (II) Repressor |
| (B) 'z' | (IV) B- Galactosidase |
| (C) 'y' | (I) Permease |
| (D) 'a' | (III) Transacetylase |
In lac operon (here lac refers to lactose), a polycistronic structural gene is regulated by a common promoter and regulatory genes. Such arrangement is very common in bacteria and is referred to as 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 protein 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. Hence, all the three gene products in lac operon are required for metabolism of lactose.