Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Molecular Basis of Inheritance

Question:

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:

Options:

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

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

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

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

Correct Answer:

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

Explanation:

The correct answer is Option (2) -A-III, B-I, C-IV, D-II

LIST I
(Genes in lac operon)

LIST II
(Products coded for)
A. i-gene III. Repressor protein
B. z-gene I. β-galactosidase
C. y-gene IV. Permease
D. a-gene II. Transacetylase

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.

In most other operons as well, the genes present in the operon are needed together to function in the same or related metabolic pathway.