1. Eukaryotic Gene Regulation
How are most eukaryotic genes controlled? In other words, how are the genes ‘told’ to turn on/off?
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2. Eukaryotic Gene Regulation
Many eukaryotic genes have a sequence called the TATA box; it is part of the promoter.
TATA
box
Upstream
enhancer
Introns
Promoter
sequences
Exons
Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase. Eukaryotic genes have regulatory sequences that are more complex than prokaryotic genes.
Direction of transcription
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3. Eukaryotic Gene Regulation
The TATA box seems to help position RNA polymerase, so that transcription can occur.
Upstream
enhancer
TATA
box
Introns
Promoter
sequences
Exons
Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase. Eukaryotic genes have regulatory sequences that are more complex than prokaryotic genes.
Direction of transcription
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4. Eukaryotic Gene Regulation
Eukaryotic promoters are usually found just before the TATA box, and consist of short DNA sequences.
Upstream
enhancer
TATA
box
Introns
Promoter
sequences
Exons
Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase. Eukaryotic genes have regulatory sequences that are more complex than prokaryotic genes.
Direction of transcription
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5. Gene products turn on/off genes
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6. Tryptophan=on/off switch
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7. 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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13. Development and Differentiation
Hox Genes are universal to animals
Fruit fly chromosome
Mouse chromosomes
Fruit fly embryo
Mouse embryo
n fruit flies, a series of hox genes along a chromosome determines the basic structure of the fly’s body. Mice have very similar genes on four different chromosomes. The color bars along the mouse’s back show the approximate body area affected by genes of the corresponding colors.
Adult fruit fly
Adult mouse
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14. Gene Regulation: An Example
How are genes turned on and off in PROKARYOTIC CELLS, like bacteria???
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15. 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 of FEEDBACK. Think of a thermostat….
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16. 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.
The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.
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17. Gene Regulation: An Example
The other region is the operator (O).
The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.
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18. Gene Regulation: An Example
When the lac repressor binds to the O region, transcription is not possible.
The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.
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19. Gene Regulation: An Example
When lactose is added, sugar binds to the repressor proteins.
The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.
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20. Gene Regulation: An Example
The repressor protein changes shape and falls off the operator and transcription is made possible.
The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.
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