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Regulation of Gene Activity

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Regulation of Gene Activity Conservation Remember, our bodies are conservative, they only make what we need, when we need it. How do they know this??? – PowerPoint PPT presentation

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Title: Regulation of Gene Activity


1
Regulation of Gene Activity
2
Conservation
  • Remember, our bodies are conservative, they only
    make what we need, when we need it.
  • How do they know this???

3
Operon
  • Jacob and Monod E. coli capable of regulating
    the expression of its genes
  • Regulator gene codes for repressor
  • Repressor controls whether the operon is active
    or not.

4
Operon
  • Promoter - DNA, beginning of gene to be
    transcribed, signals the start of a gene
  • Operator portion of DNA where repressor binds,
    controls mRNA synthesis
  • When repressor binds here, RNA polymerase cannot
    attach to the promoter, prevents transcription
  • Structural genes codes for primary structure of
    enzyme to be transcribed.

5
trp operon
  • Exist in on position repressible
  • Products 5 different enzymes, synthesis of AA
    tryptophan
  • If tryptophan is already present, it binds to
    repressor, which then binds to operator and no
    transcription takes place.

6
lac operon
  • Makes 3 enzymes needed for metabolism of lactose
  • When lactose is present, it binds to the
    repressor, and repressor cannot bind to operator,
    therefore transcription takes place
  • Lactose is an inducer, inducible operon

7
Eukaryotic regulation
  • 5 primary levels of control
  • Chromatin structure
  • Transcriptional control transcriptional factors
    initiate/regulate transcription
  • Posttranscriptional control mRNA processing and
    how fast mRNA leaves the nucleus
  • Translational control when translation begins
    and how long it continues
  • Posttranslational control after protein
    synthesis, polypeptide may have to undergo
    additional changes before it is functional.

8
Chromatin structure
  • Levels of chromatin organization is related to
    the degree that the nucleosomes coil.
  • Heterochromatin highly condensed chromatin,
    inactive
  • Barr Body- only in females, small, dark,
    condensed chromatin, inactive X chromosome
  • Euchromatin loosely compacted chromatin,
    potentially active, genes expressed.

9
Genetic mutations
  • Point mutations change in a single DNA
    nucleotide, change in specific codon
  • Frameshift muations one or more nucleotides are
    inserted or deleted
  • Nonfunctional proteins can have dramatic
    effects on phenotype

10
carcinogenesis
  • When proto-oncogenes mutate, they become
    oncogenes.
  • Tumor suppressor genes usually act to stop cell
    division if there is a problem.
  • Cancer loss of TSG and activity of oncogene
    uncontrollable cell division
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