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9 Cards in this Set
- Front
- Back
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How were temperature sensitive yeast used to discover the cdc (cell cycle dependent) gene?
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Scientists made temperature sensitive yeast with mutations in different genes. One mutation was found that arrested the cell only in G/1 S phase (aka the execution point). Another was found that arrested the phase before the G2 / M transition
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What is the cdc-2 gene in humans? What does it code for? How was it discovered?
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This the gene that is required to allow the cell to progress through the cell cycle. It codes for p34cdc2, a protein kinase. It was discovered by inserting this gene into cdc mutant yeast cells, and realizing that it they could progress through the cell cycle.
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What are cyclins? What is their role?
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They are proteins that fluctuate in levels throughout the cell cycle. They bind to p34cdc2 protein kinase (also called a cyclin dependent kinase), activating it.
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What is the mitosis promoting factor?
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This a cyclin dependent kinase (p34) with cyclin.
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What are the two main controls of p34? Why isn't p34 active in the S phase, even though there are cyclins and p34 present? Which is considered more permanent?
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The two main controls are cyclin binding to p34, and also dephosphorylating inhibitory phosphate groups on p34. Cyclin degradation is considered more permanent
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Do humans have more than one cyclin? What are some examples? How do the different types of cyclins affect p34 differently?
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Yes, humans have more than one cyclin. The G1 cyclin activates p34 during Start (the G1/S restriction point), and cyclin B activates the p34 cdc2 during G2/M checkpoint. There are also S cyclins. The type of cyclin that binds determines which substrate the kinase will affect
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What is one difference between the cdk in yeast versus in humans?
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Yeast use only one cdk for the entire cell cycle, whereas humans use different ones
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Why would the cell want to use the cyclin system? It seems like a waste to create cyclin and degrade it each time.
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It is very important to NOT replicate DNA twice, so you want to use an irreversible control, like cyclin degradation.
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How are cyclins degraded?
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They are tagged with ubiquitin, by cyclin specific ubiquitin ligases. These tagged cyclins get sent to proteosomes to be degraded
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