Q43 / 180 · NEET 2026 (Re-NEET) · Botany
Which of the following statements about lac-operon is correct ?
- AGalactose can act as an inducer of lac operon
- Correct answerBGene $i$ is constitutively expressed
- CLactose activates repressor to bind to the operator
- DGenes $i$, $z$, $y$ and $a$ share single common promoter
Solution
The $i$ gene in the lac operon codes for the repressor protein. It is a regulatory gene that is constitutively expressed, meaning it is transcribed continuously to maintain a basal level of repressor in the cell.
Galactose does not act as an inducer of the lac operon; lactose or allolactose serves as the inducer.
Lactose binds to the repressor protein and inactivates it, preventing it from binding to the operator region.
Genes $z$, $y$, and $a$ are structural genes that share a single common promoter, whereas the $i$ gene has its own separate promoter.
Answer: Gene $i$ is constitutively expressed
Galactose does not act as an inducer of the lac operon; lactose or allolactose serves as the inducer.
Lactose binds to the repressor protein and inactivates it, preventing it from binding to the operator region.
Genes $z$, $y$, and $a$ are structural genes that share a single common promoter, whereas the $i$ gene has its own separate promoter.
Answer: Gene $i$ is constitutively expressed
Hence, the correct answer is option: 'B'.