10 public questions tagged with this topic.
A repressible operon, such as the trp operon, is normally on but can be turned off when a repressor binds to it.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
The lac operon is an inducible operon that is activated in the presence of lactose to allow lactose metabolism.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
An inducible operon, like the lac operon, is normally off but can be activated by an inducer (e.g., lactose).
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
The lac operon is regulated by a repressor protein, which prevents transcription in the absence of lactose.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
An operon is a cluster of genes regulated by a single promoter, commonly found in prokaryotic cells.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
The lac operon is activated in the presence of lactose, which inactivates the repressor and allows transcription.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
The Lac operon is regulated by a repressor protein that prevents transcription in the absence of lactose.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Regulation of Gene Expression - Lac Operon
The promoter is the site where RNA polymerase binds to initiate transcription in an operon.
Ref: NCERT Class 12 Biology Chapter 5: Molecular Basis of Inheritance Transcription - Mechanism and RNA Polymerase
Operon concept formulated by François Jacob and Jacques Monod describes cluster of functionally related structural genes arranged adjacently under control of single promoter and operator transcribed together as polycistronic messenger RNA. Operons often include genes encoding proteins in same metabolic pathway like lac operon lacZYA for lactose catabolism or trp operon for tryptophan biosynthesis. Regulatory protein repressor or activator binds operator modulating polymerase access, enabling coordinate response to environmental signals. Operon organization predominates in prokaryotes, providing efficient regulatory economy absent in most eukaryotes where genes individually regulated.
Ref: Alberts Molecular Biology of Cell Chapter 7: Operon cluster genes transcribed together; Jacob Monod 1961 Lac operon theory
Polycistronic messenger RNA contains multiple consecutive open reading frames arranged linearly under single promoter control, transcribed as continuous molecule in bacteria and archaea. Each cistron retains independent ribosome binding site enabling separate translational initiation events producing distinct proteins often participating in same biosynthetic pathway, such as enzymes for amino acid synthesis. This operon structure allows coordinate induction or repression via single operator, economizes transcriptional regulation, and ensures stoichiometric co-production. Electron microscopy shows ribosomes trailing RNA polymerase translating multiple proteins simultaneously, illustrating efficient coupling of transcription and translation in polycistronic operon.
Ref: Lodish Chapter 8: Polycistronic mRNA codes multiple proteins operon example; Watson Chapter 15 Polycistronic translation
