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Related Concept Videos

Operons02:09

Operons

Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by a repressor...
Prokaryotic Transcriptional Activators and Repressors01:58

Prokaryotic Transcriptional Activators and Repressors

The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
Transcription of prokaryotic...
Operons02:09

Operons

Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by a repressor...
Prokaryotic Transcriptional Activators and Repressors01:58

Prokaryotic Transcriptional Activators and Repressors

The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
Transcription of prokaryotic...
Operon Model01:23

Operon Model

The operon model represents a fundamental mechanism of gene regulation in prokaryotes, enabling coordinated expression of genes involved in related metabolic or functional pathways. Operons consist of structural genes, a promoter, and an operator, with transcription regulated by repressors, activators, and small effector molecules.Structure and Function of OperonsAn operon is a cluster of structural genes transcribed together under the control of a single promoter. The promoter region...
Inducible Operons: lac Operon01:25

Inducible Operons: lac Operon

The lac operon in Escherichia coli is a model for understanding inducible gene regulation and metabolic flexibility. It integrates local control by lactose and global regulation through catabolite repression, enabling E. coli to preferentially metabolize glucose when available and switch to lactose utilization when glucose is scarce.Structure and Function of the lac OperonThe lac operon contains three structural genes: lacZ (β-galactosidase), lacY (lactose permease), and lacA (thiogalactoside...

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Related Experiment Video

Updated: Jun 1, 2026

Localization of Odorant Receptor Genes in Locust Antennae by RNA In Situ Hybridization
09:30

Localization of Odorant Receptor Genes in Locust Antennae by RNA In Situ Hybridization

Published on: July 13, 2017

How lambda repressor and lambda Cro distinguish between OR1 and OR3.

A Hochschild, J Douhan, M Ptashne

    Cell
    |December 5, 1986
    PubMed
    Summary
    This summary is machine-generated.

    Bacteriophage lambda repressor and Cro proteins distinguish between DNA operator sequences. Specific amino acids in the proteins and base pairs in the operators determine these recognition preferences.

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    Last Updated: Jun 1, 2026

    Localization of Odorant Receptor Genes in Locust Antennae by RNA In Situ Hybridization
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    Published on: July 13, 2017

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    Visualizing the Interaction Between the Qdot-labeled Protein and Site-specifically Modified λ DNA at the Single Molecule Level
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    Published on: July 17, 2018

    Area of Science:

    • Molecular Biology
    • Genetics
    • Protein-DNA Interactions

    Background:

    • Lambda repressor and lambda Cro proteins bind to shared operator sites on the phage chromosome.
    • These proteins exhibit distinct binding preferences for specific operator sequences (OR1 and OR3).

    Purpose of the Study:

    • To investigate the molecular basis for the differential binding specificities of lambda repressor and Cro proteins.
    • To identify key amino acid residues and DNA base pairs responsible for discriminating between operator sequences.

    Main Methods:

    • Site-directed mutagenesis was employed to alter base pairs within the operator sequences.
    • Amino acid substitutions were introduced into the recognition helices and amino-terminal arms of the repressor and Cro proteins.
    • Binding affinities were analyzed to determine the impact of these modifications on protein-DNA interactions.

    Main Results:

    • Protein preferences are dictated by residues 5 and 6 of the recognition helices and the amino-terminal arm (for repressor).
    • Key DNA operator positions for discrimination are position 3 (for Cro) and positions 5 and 8 (for repressor).
    • Specific amino acid-protein and base-pair interactions underpin the distinct recognition capabilities of repressor and Cro.

    Conclusions:

    • The study elucidates the molecular mechanisms by which lambda repressor and Cro achieve sequence-specific DNA binding.
    • These findings contribute to a deeper understanding of how related proteins can evolve distinct DNA recognition profiles.
    • The identified residues and base pairs are critical determinants of operator discrimination.