Download differential gene expression

Agenda 3/22
• Stickleback switches video
• Stickleback switches model and activity
Homework: Gene expression essay (due
3/23)
Turn in: Video notes
Warm up: How does DNA organization differ
in eukaryotes and prokaryotes?
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• How is eukaryotic gene expression
different than prokaryotic gene
expression?
• How do our cells become different and
specialized?
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Agenda 3/23
• Eukaryotic control lecture
• Lactase click and learn
• Homework: Development Video and Notes
*, Finish Essay
• Turn in: Nothing ...unless essay is finished
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Control of Eukaryotic
Gene Expression
Eukaryotic Gene Regulation
Prokaryotic regulation is different from eukaryotic
regulation.
1. Eukaryotic cells have many more genes (23,700 in
human cells) in their genomes than prokaryotic
cells (average 3000).
2. Physically there are more obstacles as eukaryotic
chromatin is wrapped around histone proteins.
3. There are more non-histone proteins that are used
in eukaryotic gene expression than in prokaryotic
gene expression.
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Eukaryotic Gene Regulation in
Multicellular Organisms
• Almost all the cells in an organism are
genetically identical or totipotent.
• Differences between cell types result from
differential gene expression -- the
expression of different genes by cells with
the same genome.
• Errors in gene expression can lead to
diseases including cancer.
• Gene expression is regulated at many
stages.
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Organization
of DNA
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Three Levels of Control
• 1. Pre-transcriptional
– Methylation
– Acetylation
– Transcription factors
• 2. Post-transcriptional
– Alternative splicing
• 3. Post-translational
– ubiquitination
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Epigenetics
• Epigenetics refers to processes that
influence gene expression or function
without changing the underlying DNA
sequence.
1. Acetylation
2. Methylation
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Acetylation
• Acetylation of lysine found on the histone decreases the
affinity of histones for DNA and other histones, thereby
making DNA more accessible for transcription.
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Methylation
• A methyl group can be added to the nitrogenous bases of
cytosine that are followed by guanine
• Different cells have different methylation patterns, which
contributes to the differences in gene expression in different
cell types.
• Methylation makes DNA less likely to be transcribed
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The role of enhancers and
transcription factors.
• a. Transcription factors bind to the promoter
region (TATA box) for the RNA polymerase to
attach.
• b. Inducer regions which may help transcription
factors to bind.
• c. DNA site control elements even further
upstream (thousands of nucleotides away)
called a enhancers.
– DNA enhancers can work by a protein (activator)
attaching to the enhancer.
– The DNA then loops the DNA back on itself to attach
to the promoter region.
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Role of Transcription Factors
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Role of Transcription
Factors and Activators
• This illustrates how
different cells have
different activators
which activate
different genes.
• The liver cells need
the protein albumin
and not the protein
crystallin and the
lens cells do not
need albumin but do
need crystallin.
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Post-Transcriptional Control
Alternative Splicing
Alternative splicing
• Once the immature mRNA is made, it could be
processed in different ways to give rise to different
mature mRNA and thus different proteins.
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Example of Alternative Splicing the
Same Gene in Humans
• There are 23,700 protein-coding genes in the human
genome; BUT they are responsible for producing about
160,000 different proteins. This is possible due to
alternative splicing during RNA Processing. Each protein
coding gene has an average of 7 different products. 95%
of human genes undergo alternative splicing.
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Post-translational
control- Ubiquitin
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