Lac Operon Genes and Their Products — NEET Biology
✅ Asked in NEET 2026The 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. 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.
NTA repeatedly tests the gene-product mapping in the lac operon. The most common trap is confusing which gene codes for which enzyme — students mix up the z gene (beta-galactosidase) with the y gene (permease). This paragraph has been tested 7 times in NEET from 2019 to 2026 — always targeting the same gene-product relationships. Memorise: z = beta-galactosidase, y = permease, a = transacetylase, i = repressor.
This paragraph was tested 7 times in NEET.
In the lac operon, the z gene codes for
The lactose present in the growth medium of bacteria is transported to the cell by the action of:
Given below are two statements: Statement I: In the lac operon, the z gene codes β-galactosidase which is primarily responsible for the hydrolysis of lactose into galactose and glucose. Statement II: In addition to lactose, glucose or galactose can also induce the lac operon.
In the lac operon, the i gene codes for:
Match List I with List II: (NEET 2023) List I List II A. gene ‘a’ I. β-galactosidase B. gene ‘y’ II. Transacetylase C. gene ‘i’ III. Permease D. gene ‘z’ IV. Repressor protein
In lac operon, z gene codes for: (NEET 2022 Phase 2)
Match the following genes of the Lac operon with their respective products: (NEET 2019) (A) i gene – (i) β-galactosidase (B) z gene – (ii) Permease (C) a gene – (iii) Repressor (D) y gene – (iv) Transacetylase
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