Problem Set 7 Flashcards
(32 cards)
If a yeast cell in G1 in moved from rich medium to a low nutrient medium, the cell will likely..
Stay in G1 longer until it reaches the normal size to enter S phase
What controls the phosphorylation events that regulate the cell cycle?
The action of a kinase that requires bound cyclin for its activity
Once the signal that directs a cell to move from G1 to S phase has been generates, what does the cell do?
the cell replicates its DNA
When G1 phase cells are S phase cells are fused together, the G1 nucleus begins to replicate DNA. What can be drawn from this result?
S phase cytoplasm contains diffusible factors that stimulate the initiation of DNA synthesis
As concentrations of cyclin increases in the cell,
CDK binds the cyclin subunit and is activated
What do CDKs do just before the end of G2 to initiate the events leading to mitosis?
Phosphorylate substrates needed for cell to enter mitosis
In addition to cyclin, what else contributes to CDK activation?
Phosphorylation at an activating site on the CDK and the removal of an inhibitory phosphate group from CDK
What leads to a halt in the progress of the cell cycle?
When chromosomal DNA damaged and when DNA replication is not completed
What kind of interaction attacked polyubiquitin to the target protein?
Covalent interactions
What would be likely to happen to yeast cells in G1 if you were able to treat them with an inhibitor that specifically inactivated its only CDK?
The cells would remain in G1 and would not progress toward mitosis
The catalytic subunit of maturation-promoting factor…
transfers a phosphate group from ATP to certain a.a of specific substrates
AND
converts ATP to ADP
If you made a temp sensitive mutation that made mammalian CDK1 inactive at 42.C, what would happen to the cells at 42.C?
They would be stuck in G2 with replicated DNA
If you made a temp sensitive mutation that inactivated cyclin D at 42.C, what would happen to the cell at 42.C?
they would accumulate at G1
If you made a temp sensitive mutation in CDK2, what would happen to the cells when you shift to the restrictive enzyme?
they would be stuck in G1 or S phase
assume CAK normally does not phosphorylate CDK until Wee1 has added its phosphate. if you made a temp sensitive mutation in yeast that made CAK able to phosphorylate CDK at any time at restrictive temp, what would happen?
They would be smaller than normal
Cdc25 is normally regulated by nutritional and other environmental factors to allow activation of cyclin/cdk at appropriate time. if you made a mutation in yeast Cdc25 that removed this regulation and made the enzyme always active at the restrictive enzyme, what would be the response?
The cells would be unusually small
if you made a temp sensitive mutation in Wee1 kinase that made the enzyme hyperactive at the restrictive temp, what would be the result?
the cells would be unusually large
if you made a mutation that knocked out Cdc25 function, what would happen to the cells?
The cells would grow abnormally large
The stage that is not in the cell cycle is…
Go
The stages of the cell cycle that are included in interphase
G1, S, and G2
The stage of the cell cycle in which proteins needed for cell division would likely be made is…
G2
You observe a cell line growing on a culture dish. The cells cover the entire surface of the dish and cell division ceases. You scrape and remove a circle of cells from the center of the disk. Cells bordering the cell start dividing and running through what appears to be a normal cell cycle. What phase of the cycle were they in before the circle of cells were removed?
Go
What triggers the entry of a cell into mitosis?
the removal of inhibitory phosphate group from Cdk by Cdc25 phosphatase
During degradation of the specified protein…
ubiquitin protein ligases mediate addition of ubiquitin chains to cyclins and APC/C recognizes a conserves destruction box seq in mitotic cyclins and promotes their polyubiquitin
