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#repressible operon

3 public questions tagged with this topic.

BOTANY

Which of the following is correct about a repressible operon?

A **repressible operon, such as the trp operon, is normally on but can be turned off when a repressor binds to it**. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Botany section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Botany portion (Latest NCERT Textbooks for Academic Session 2026-27 -

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Gene regulation in Prokaryotes

Tryptophan operon is an example of

Tryptophan operon serves biosynthetic anabolic role synthesizing essential amino acid from simple chorismate precursor, consuming substantial energy and nitrogen resources. Regulation as repressible system reflects cellular economy: when intracellular tryptophan abundant through uptake from environment or previous synthesis, further production becomes wasteful and should cease. Operon normally remains transcribed, with trpR gene encoding aporepressor protein that becomes functionally active only after binding tryptophan co-repressor molecule. This architecture contrasts sharply with inducible

Ref: NCBI Bookshelf The Cell – Transcription in Prokaryotes: trp operon contains five biosynthetic genes, repressible by TrpR.

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