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Home Questions 6BJH22R9DB
Target Exam

CUET

Subject

Biology

Chapter

Principles of Inheritance and Variation

Question:

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:

Options:

(A)-(IV), (B)-(II), (C)-(III), (D)-(I)

(A)-(I), (B)-(III), (C)-(II), (D)-(IV)

(A)-(II), (B)-(IV), (C)-(I), (D)-(III)

(A)-(III), (B)-(IV), (C)-(I), (D)-(II)

Correct Answer:

(A)-(II), (B)-(IV), (C)-(I), (D)-(III)

Explanation:

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.

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