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Eukaryotic Gene Expression

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Eukaryotic Gene Expression Why is gene regulation more complex in eukaryotes than prokaryotes? Eukaryotes have larger more complex genome Eukaryotic DNA must be more ... – PowerPoint PPT presentation

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Title: Eukaryotic Gene Expression


1
Eukaryotic Gene Expression
  • Why is gene regulation more complex in eukaryotes
    than prokaryotes?
  • Eukaryotes have larger more complex genome
  • Eukaryotic DNA must be more highly organized than
    prokaryotic DNA

2
Prokaryotic vs. Eukaryotic DNA
  • Prokaryotic DNA
  • circular
  • smaller than eukaryotic DNA
  • associated with very few proteins
  • less structured and folded
  • Eukaryotic DNA
  • associated with lots of histone proteins to form
    chromatin fiber
  • very extended and tangled during interphase
  • condensed into discrete chromosomes during mitosis

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Eukaryotic Development
  • Cellular differentiation is the specialization of
    cells during development
  • Since all cells have the same DNA, how can
    differentiation occur?
  • Gene regulation.

8
Selective Gene Expression
  • How do cells become specialized?
  • Different genes are activated at different times
    during development.
  • Each cell utilizes only about 3 of genome

9
DNA PackingHelps regulate gene expression
  • DNA in one human cells 46 chromosomes would be 3
    meters long.
  • How, then, does it all fit into the nucleus?
  • DNA packing
  • Why do densely packed regions of chromosomes
    inactivate gene expression?
  • RNA pol cant get to the gene for transcription.

10
  • What is the difference between heterochromatin
    and euchromatin?
  • Heterochromatin remains highly condensed even
    during interphase
  • Barr bodies are X chromosomes condensed into
    heterochromatin
  • Telomeres, centromeres also heterochromatin
  • euchromatin is chromatin that is not condensed
    and can be transcribed

11
Control of Gene Expression
  • What are the steps from chromosome to functional
    protein?
  • Unpacking ?Transcription? mRNA processing ?
    export from the nucleus ? translation ? protein
    modification
  • ANY of these steps can be regulated in eukaryotes

12
Chromatin modification
  • DNA methylation the addition of methyl groups to
    DNA
  • essential for inactivation of the DNA
  • Inactive genes in a cell are methylated
  • Epigenetic memory due to methylating enzymes that
    methylate the new daughter strand the same as the
    parent strand.
  • Can be passed on in repro
  • Histone acetylation is the attachment of an
    acetyl group to histone proteins
  • acetylation increases likelihood for
    transcription of the DNA

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Transcriptional Control
  • Transcription factors allow RNA pol to find the
    promoter region
  • association between transcriptional factors and
    enhancer or promoter region regulates gene
    expression

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Posttranscriptional control
  • Regulation of RNA processing
  • Regulation of mRNA degradation
  • Can last from hours to weeks
  • Regulation of translation
  • initiation sequence can be blocked
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