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    Gene Expression and Regulation

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    gengkapak
    Gene expression and regulation involves transcription of DNA to RNA and translation of RNA to protein. Transcription requires a promoter, auxiliary factors like sigma factor, RNA polymerase, and ribonucleotides. Translation involves mRNA binding to ribosomes with tRNAs and auxiliary factors to produce proteins based on genetic codes. Gene regulation controls gene expression and allows rapid switching between biochemical pathways. The lac operon model in prokaryotes demonstrates regulation via an active repressor that binds to the operator to inhibit transcription in the absence of an inducer like lactose. This provides an early example of an operon regulatory system.

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    Gene Expression and Regulation

    Uploaded by

    gengkapak
    145 views27 pages
    Gene expression and regulation involves transcription of DNA to RNA and translation of RNA to protein. Transcription requires a promoter, auxiliary factors like sigma factor, RNA polymerase, and ribonucleotides. Translation involves mRNA binding to ribosomes with tRNAs and auxiliary factors to produce proteins based on genetic codes. Gene regulation controls gene expression and allows rapid switching between biochemical pathways. The lac operon model in prokaryotes demonstrates regulation via an active repressor that binds to the operator to inhibit transcription in the absence of an inducer like lactose. This provides an early example of an operon regulatory system.

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    Gene expression and regulation involves transcription of DNA to RNA and translation of RNA to protein. Transcription requires a promoter, auxiliary factors like sigma factor, RNA polymerase, and ribonucleotides. Translation involves mRNA binding to ribosomes with tRNAs and auxiliary factors to produce proteins based on genetic codes. Gene regulation controls gene expression and allows rapid switching between biochemical pathways. The lac operon model in prokaryotes demonstrates regulation via an active repressor that binds to the operator to inhibit transcription in the absence of an inducer like lactose. This provides an early example of an operon regulatory system.

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    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    145 views27 pages

    Gene Expression and Regulation

    Uploaded by

    gengkapak
    Gene expression and regulation involves transcription of DNA to RNA and translation of RNA to protein. Transcription requires a promoter, auxiliary factors like sigma factor, RNA polymerase, and ribonucleotides. Translation involves mRNA binding to ribosomes with tRNAs and auxiliary factors to produce proteins based on genetic codes. Gene regulation controls gene expression and allows rapid switching between biochemical pathways. The lac operon model in prokaryotes demonstrates regulation via an active repressor that binds to the operator to inhibit transcription in the absence of an inducer like lactose. This provides an early example of an operon regulatory system.

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    Download as ppt, pdf, or txt
    of 27

    Gene Expression and

    Regulation
    Functional Interaction Among
    Biomolecules
    Gene expression
    • Genotype to Phenotype
    • DNA to RNA to Protein (Central
    Dogma)
    • Transcription: DNA (gene) to RNA
    • Translation: mRNA to polypeptide
    • Basic and simplified system –
    Prokaryotes (Escherichia coli)
    Requirements for Gene
    transcription
    • Promoter sequences (Pribnow box)
    and others
    • Auxilliary factors (sigma  and rho)
    • RNA polymerase (core enzyme)
    • Holoenzyme (core enzyme + 
    factor)
    • Free ribonucleotides
    Where to start?

    Holoenzyme
    (21 + )
    Transcription Initiation
    Transcription Elongation
    Transcription Termination

    rho
    Gene translation
    • Information of triplet base (Codon):
    Genetic Codes
    • Involves recognition of codon (in
    mRNA) by anticodon (in tRNA)
    • Requires ribosome (small and large
    subunits)
    • Requires auxilliary factors: initiation,
    elongation, and termination factors
    What is the Genetic Code?
    What are Ribosomes?
    Translation Initiation 1

    The general rule of translation initiation: Protein


    synthesis always starts with methionine codon
    (AUG)
    Translation Initiation 2
    Translation Elongation
    Translation Elongation (Peptide bond)
    Translation Termination
    Gene Regulation
    The lac Operon Model
    (Prokaryote System)
    What is Gene Regulation?
    • Natural mechanism to control gene
    expression
    • Reversible system: Allows rapid
    switches from one biochemical
    pathway to another
    • Usually short-term
    • Purposes: 1) Development and
    growth
    2) Adaptation to
    environment
    Understanding some terminologies…
    • Operons: Transcriptional units (bacterial
    genes) that contain more than one coding
    sequence
    • lac operon: A single transcriptional unit
    encoding three enzymes for lactose
    metabolism (Francois Jacob and Jacques
    Monod @ Pasteur Institute in Paris, 1950s)
    • Regulatory genes: Produce repressors or
    activators
    • Operator: Segment of DNA that is
    recognized and bound by regulatory
    proteins
    Operon Model (Jacod-Monod
    Hypothesis)
    -galactosidase – hydrolyzes lactose into glucose and
    galactose

    Galactoside permease – promotes transport of lactose


    and related sugars into cell

    Thiogalactoside transacetylase – function(s) unclear


    Regulation by Active Repressors

    • Regulatory protein involved is lac


    repressor (isolated and purified in
    1967 by Gilbert and Muller-Hill)
    • Active repressor: Binds to a site
    within the promoter (operator) and
    inhibits transcription of the lac
    operon
    • lac repressor has domain that can
    bind to chemical derivatives of
    lactose (inducer)
    lac repressor system
    Regulation by Inactive Repressors

    • Regulatory protein involved is trp


    repressor
    • Operates in the trp operon:
    transcriptional unit encoding
    enzymes for the biochemical
    pathway synthesizing the amino
    acid, tryptophan
    • trp repressor has domain can bind
    to tryptophan (corepressor)
    The trp operon
    The trp repressor system
    Summary of
    Operon
    Regulatory
    System

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