Regulation of Gene Expression Eukaryotes - PowerPoint PPT Presentation

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Regulation of Gene Expression Eukaryotes

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Title: Regulation of Gene Expression Eukaryotes


1
Regulation of Gene ExpressionEukaryotes
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I. Regulation at Stages
  • A. All organisms prokaryotes and eukaryotes alike
    have to regulate which genes are expressed.
  • 1. both uni- and multicellular organisms must
    continually turn genes on and off in response to
    signals
  • B. All cells have the same genome however, the
    genes expressed by each cell is unique allowing
    for cells to carry out specific functions.
  • 1. Cells do not differ in genes present but
    differential gene expression

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II. Eukaryotes Gene Expression
  • A. To express a gene through protein synthesis
    there are several control points which gene
    expression can be turned on or off
  • 1. The most common point is during transcription.
    Coming as a response to signals coming from
    outside the cell.
  • 2. But it can be controlled along the structure
    of the chromosome, during initiation complex, RNA
    editing, attachment on ribosome, translation and
    protein processing.

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III. Regulation of Chromatin Structure
  • A. Along our cells our DNA is condensed into
    tightly packed chromatin made up of units called
    nucleosomes.
  • 1. The location of a gene on the nucleosomes can
    affect how its expressed.
  • B. Histones the proteins that DNA is wrapped
    around can allow some enzymes (transcription
    factors) to bind and allow access to genes.
    Depending on if the histone is acetylated this
    causes histones to be loosely packed. If not
    acetylated chromosome is densely packed
    preventing the DNA from being read.

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  • C. DNA methylation regions of DNA that are
    usually not transcribed, inactivated genes due to
    the addition of the methyl groups. If they are
    removed DNA can then turn on these genes.
  • D. Both DNA methylation histone acetylation are
    examples of epigenetic inheritance traits
    transmitted by the mechanisms not directly
    involving the sequence.

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IV. Regulation of Transcription Initiation
  • A. There are several control elements that allow
    for transcription to occur including
  • 1. transcription factors
  • 2. RNA polymerase
  • 3. enhancers affected by activators or
    repressors
  • 4. mediated proteins
  • B. The specific way when enhancers are activated
    (several different ways)are then folded along the
    DNA to mediated proteins which will interact with
    the promoter to help assemble the initial complex
    to start transcription.

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Mediated proteins
Transcription factors
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V. Transcription Between the classes of cells
  • A. Unlike prokaryotes that have all the genes for
    a specific function all located close together on
    an operon to be transcribed by one enzyme
    starting from one promoter site.
  • B. Eukaryotes that are going to express several
    genes together (co-expressed) are scattered along
    several chromosomes. So several activators need
    to recognize the control elements along those
    chromosomes to allow for simultaneous
    transcription.

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VI. Post-Transcriptional Regulation
  • A. After transcription the mRNA can be
    alternatingly spliced changing which sections are
    treated as exons and introns by regulatory
    proteins.

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VII. mRNA Degradation
  • A. mRNA molecules in eukaryotes have a fairly
    long life span and can be translated several
    times before it is degraded.

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VIII. Regulation of Translation
  • A. Regulatory proteins can prevent mRNA from
    attaching correctly to the ribosome preventing
    translation.
  • B. Protein factors can also activate or
    inactivate translation for ALL mRNA molecules in
    a cell at the same time.

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IX. Regulation Along Protein Processing
  • A. Some proteins in order to function properly
    need to undergo chemical modifications. Others
    have to be folded to begin working and still many
    proteins need to be transported to a specific
    location in the cell to begin functioning
    correctly.
  • 1. At every point proteins can be regulated
  • B. How long each protein functions can also be
    regulated by selective degradation.
  • 1. Ubiquitin a small protein marks other proteins
    for degradation by proteasomes.

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