Match List-I with List-II.
| List-I | List-II |
|---|---|
| A. z gene | I. Permease |
| B. y gene | II. Repressor |
| C. a gene | III. Beta-galactosidase |
| D. i gene | IV. Transacetylase |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-I, C-IV, D-II
The lac operon has one regulatory gene (i) and three structural genes (z, y and a). Each gene makes one protein, and all three structural gene products are needed for the metabolism of lactose.
(A) z gene — this matches (III) Beta-galactosidase, which hydrolyses lactose into galactose and glucose.
(B) y gene — this matches (I) Permease, which increases the permeability of the cell to β-galactosides.
(C) a gene — this matches (IV) Transacetylase.
(D) i gene — this matches (II) Repressor. Here i comes from inhibitor, not inducer.
The correct code is A-III, B-I, C-IV, D-II.
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.”