Transcript 12-5 Gene Regulation

12-5 Gene Regulation
Eukaryotic Gene Regulation
How are most eukaryotic genes
controlled?
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12-5 Gene Regulation
Eukaryotic Gene Regulation
Many eukaryotic genes have a sequence called the
TATA box; it is part of the promoter.
Upstream
enhancer
TATA
box
Promoter
sequences
Introns
Exons
Direction of transcription
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12-5 Gene Regulation
Eukaryotic Gene Regulation
The TATA box seems to help position RNA
polymerase, so that transcription can occur.
Upstream
enhancer
TATA
box
Promoter
sequences
Introns
Exons
Direction of transcription
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12-5 Gene Regulation
Eukaryotic Gene Regulation
Eukaryotic promoters are usually found just before
the TATA box, and consist of short DNA sequences.
Upstream
enhancer
TATA
box
Promoter
sequences
Introns
Exons
Direction of transcription
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12-5 Gene Regulation
Development and Differentiation
Development and Differentiation
As cells grow and divide, they undergo
differentiation, meaning they become specialized
in structure and function.
Hox genes control the differentiation of cells and
tissues in the embryo.
They are master genes—lay out the body plan;
tell other genes to do their thing
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Development and Differentiation
Hox Genes are universal to animals
Fruit fly chromosome Mouse chromosomes
Fruit fly embryo
Mouse embryo
Adult fruit fly
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Adult mouse
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12-5 Gene Regulation
Gene Regulation: An Example
How are genes turned on and off in PROKARYOTIC
CELLS, like bacteria???
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12-5 Gene Regulation
Gene Regulation: An Example
Bacteria turn on/off genes, too. An
example of this are the “lac” genes
The lac genes (genes to use lactose) are turned off
by repressors and turned on by the presence of
lactose. You only want to make the digestive
proteins when needed….
Thus, being able to turn on/off genes is an example
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of FEEDBACK. Think of a thermostat….
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12-5 Gene Regulation
Gene Regulation: An Example
On one side of the operon's three genes are two
regulatory regions.
• In the promoter (P) region, RNA polymerase
binds and then begins transcription.
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12-5 Gene Regulation
Gene Regulation: An Example
• The other region is the operator (O).
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12-5 Gene Regulation
Gene Regulation: An Example
When the lac repressor binds to the O region,
transcription is not possible.
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12-5 Gene Regulation
Gene Regulation: An Example
When lactose is added, sugar binds to the repressor
proteins.
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12-5 Gene Regulation
Gene Regulation: An Example
The repressor protein changes shape and falls off the
operator and transcription is made possible.
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