Ch 15 - .Gene Regulation

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Ch 15 - .Gene Regulation

• Prokaryote Regulation
• Operon not found in eukaryotes
• Regulator gene codes for repressor. Active
  repressor binds to operon
• Promoter where RNA polymerase attaches

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2 types of regulators

• Repressible operon
• 1 always on repressor cannot bind,
  therefore RNA polymerase can attach and protein
  is made.
• Ex. Trp operon
• -To turn off the protein product binds to
  repressor repressor can bind transcription
  ceases

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Inducible Operon

• 2 always off repressor can always bind
  therefore RNA polymerase cannot attach no
  protein produced
• Ex. Lac operon

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Presence of molecule (inducer) turns on
transcription by binding to lac repressor to
disable binding.
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Eukaryotic Regulation

• allows differential protein expression
  dependent on specialized function of cell.
• 5 ways 3 within the nucleus 2 in the
  cytoplasm

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• 1 chromatin structure packaging makes RNA
  epigenetic polymerase binding impossible
  cancer results when mutations occur in
  transcriptional factor genes.

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2 Transcriptional control transcription
factors- proteins that initiate RNA pol. binding
once a gene is unpackaged it will be transcribed.
(transposons shut down genes by interrupting
code, gene jumping, also encourages mutations)
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3 posttranscriptional control-mRNA processing
excising introns
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4 - translational control poly a tail
protects mRNA from being degraded allows for
translation
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(No Transcript)
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5 - Posttranslational control modification of
a protein after synthesis determines biological
activity.
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Chromatin Structure

• DNA wrapped around 8 histones
• DNA histone nucleosomes
• Highly condensed heterochromatin inactive,
  methyl groups
• Loosely condensed euchromatin active have
  attached acetyl group. DNA can be methylated
  not expressed can be inherited that way

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KINASES

• Proteins that dephosphorylate to signal protein
  expressions in membrane to nucleus regulatory
  pathway

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TRANSPOSONS

• Jumping genes of repetitive sequence that
  interrupt gene expression

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GENETIC MUTATIONS- good, bad, non effective

• 1-germline ? passed on
• 2- somatic ? not passed on ? cancer

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MUTATIONS causes- spontaneous, environ.
mutagens, inherited0

• Point Mutations- Change a single base? change
  codon
• Frame shift mutations- deletion or addition
  result in a completely new amino acid sequence.
• Mutations in proto-oncogenes or tumor suppressor
  ?cancer

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Study Questions

• What part of mRNA sections are spliced together
  into the finished mRNA molecules?
• What are 4 potential control mechanisms for
  regulation of gene expression in eukaryotic
  organisms?
• What is the correct order of protein synthesis?

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Study Questions

• What is the role of DNA in controlling cellular
  activity?
• What word describes the attachment of groups of
  particular amino acids of specific proteins to
  nucleosomes as thought to be an important control
  mechanism for gene expression?
• Define the term gene

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Study Questions

• The expression of genes can be controlled at what
  4 stages of protein synthesis?