Question:
Who proposed 'Operon' model for gene regulation in bacteria?
Who proposed 'Operon' model for gene regulation in bacteria?
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Remember that the lac operon is an inducible operon (turned on in the presence of lactose).
In contrast, the trp (tryptophan) operon is a repressible operon (turned off in the presence of tryptophan).
In contrast, the trp (tryptophan) operon is a repressible operon (turned off in the presence of tryptophan).
Updated On: Jul 13, 2026
- Sanger
- Watson and Crick
- James and Monad
- Jacob and Monad
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The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
An operon is a functional unit of genomic DNA in prokaryotes containing a cluster of genes under the control of a single promoter.
This organization allows genes involved in the same metabolic pathway to be transcribed together into a single polycistronic mRNA transcript.
Step 3: Detailed Explanation:
The Operon model of gene regulation was proposed by French scientists François Jacob and Jacques Monod in 1961.
They studied lactose metabolism in Escherichia coli and characterized the lactose (lac) operon.
Their model showed that gene expression is regulated by physical interactions between:
1. Structural genes: Coding for metabolic proteins (such as lacZ, lacY, and lacA).
2. Promoter: The DNA sequence where RNA polymerase binds.
3. Operator: A DNA sequence between the promoter and structural genes where a repressor protein can bind.
4. Regulatory gene: Coding for a repressor protein that can block transcription by binding to the operator.
Jacob and Monod's discovery established the concept of transcriptional control, for which they were awarded the Nobel Prize in Physiology or Medicine in 1965.
Let us evaluate the other options:
- Sanger (A) is famous for developing DNA sequencing techniques.
- Watson and Crick (B) discovered the double-helix structure of DNA.
Therefore, Jacob and Monod proposed the operon model.
Step 4: Final Answer:
The Operon model was proposed by Jacob and Monod, matching Option (D).
An operon is a functional unit of genomic DNA in prokaryotes containing a cluster of genes under the control of a single promoter.
This organization allows genes involved in the same metabolic pathway to be transcribed together into a single polycistronic mRNA transcript.
Step 3: Detailed Explanation:
The Operon model of gene regulation was proposed by French scientists François Jacob and Jacques Monod in 1961.
They studied lactose metabolism in Escherichia coli and characterized the lactose (lac) operon.
Their model showed that gene expression is regulated by physical interactions between:
1. Structural genes: Coding for metabolic proteins (such as lacZ, lacY, and lacA).
2. Promoter: The DNA sequence where RNA polymerase binds.
3. Operator: A DNA sequence between the promoter and structural genes where a repressor protein can bind.
4. Regulatory gene: Coding for a repressor protein that can block transcription by binding to the operator.
Jacob and Monod's discovery established the concept of transcriptional control, for which they were awarded the Nobel Prize in Physiology or Medicine in 1965.
Let us evaluate the other options:
- Sanger (A) is famous for developing DNA sequencing techniques.
- Watson and Crick (B) discovered the double-helix structure of DNA.
Therefore, Jacob and Monod proposed the operon model.
Step 4: Final Answer:
The Operon model was proposed by Jacob and Monod, matching Option (D).
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