Term
| What are the two key events involved in the cell cycle? |
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Definition
Replicate chromosomal DNA once and put identical replicas of each chromosome into two daughter cells |
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Term
| What are some major things to note in general about the cell cycle? |
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Definition
The cell cycle is under genetic control, the cell cycle can't be reversed, many genes are transcribed during the cell cycle right before their products are needed and mutations affecting the cell cycle have helped to identify the key regulatory pathways (and cancers) |
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Term
| What are some important things to note about the buds that come off of parent yeast cells during cell replication? |
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Definition
The bud first emerges shortly after DNA synthesis begins. At the onset of mitosis, the bud is almost as large as the mother cell. After separation and completiong of mitosis the bud cell must grow to reach a certain size before it can start its own mitosis cycle |
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Term
| What is the cell cycle regulated by? |
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Definition
| The cell cycle is regulated by cyclins and cyclin-dependent protein kinases (CDKs) |
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Term
| What do cyclin-CDK complexes do in regards to target proteins? |
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Definition
| They change their activity level (positively or negatively) |
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Term
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Definition
A mitogen is a chemical or some sort of treatment that stimulates the mitotic cell cycle |
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Term
| What are four key things to remember about cyclin dependent kinases (CDKs)? |
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Definition
They're only active when bound to a cyclin, specific CDK-cyclin complexes trigger progression through each stage of the cell cycle, kinases add a phosphate to the target protein and adding or taking away a phosphate changes the shape (and therefore the function) of a protein |
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Term
| What two cyclins are typically present during the G1 stage of the cell cycle? |
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Definition
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Term
| What cyclin is normally found primarily towards the end of the G1 cycle heading into the S stage? |
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Definition
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Term
| What cyclin is typically found during the S phase of the cell cycle? |
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Definition
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Term
| What cyclin is typically found during the beginning of the G2 phase of the cell cycle? |
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Definition
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Term
| How do cyclins control the G1 to S phase transition? |
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Definition
1. Growth factor activates the signaling cascade. 2. Cyclin D is expressed. 3. CyclinD/CDK4&6 phosphorylates the retinoblastoma (RB) protein to form pRB. 4. pRB lets go of the E2F transcription factor. 5. E2F goes into the nucleus and activates the transcription of cyclin E and then cyclin A later. 6. Cyclin E and CDK2 drive the cycle into the S phase |
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Term
| What will happen in regards to the cell cycle if the retinoblastoma protein remains active and unphosphorilated? |
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Definition
The cell will remain in the G1 phase until the cell becomes large enough so that it can enter the S phase |
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Term
| What do cyclins and CDKs do in regards to promotion of DNA replication? |
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Definition
They promote replication. CDC6 and proteins of the replication complex bind to the origins of replication and CDC6 is taken off by phosphorilation (which also initiates DNA replication) |
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Term
| What cyclin is progression from the G2 into the M pase dependent on? |
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Definition
The B-CDK2 complex known as maturation-promoting complex |
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Term
| What is proteolysis and how does this help the cell cycle? Give one example of this |
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Definition
Proteolysis is the degradation of proteins used in the preceding phase as well as proteins that would inhibit progression of the cycle into the next phase. The anaphase-promoting complex (APC/C) adds a 76-amino-acid protein ubiquitin to target proteins which mark them for destruction in the proteasome |
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Term
| How do cell cycle checkpoints work? |
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Definition
Cells can monitor their internal and external environments and they maintain the correct order of steps as they go through the cycle. Cells can pause when defects are detected so that these issues can be fixed if possible. Once these checkpoints are passed the cell is either clear to go on with the cycle or will self-destruct |
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Term
| What are the three major checkpoints involved in the cell cycle (that is, what do they mainly relate to?) |
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Definition
There is the DNA damage checkpoint, the centrosome duplication checkpoint and the spindle checkpoint |
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Term
| What does the DNA damage checkpoint do to prevent potential problems? |
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Definition
The checkpoint arrests the cell cycle when DNA is damaged or when replication isn't completed. The three points when the DMA damange checkpoint is used is at the G1/S transition, in the S period and at the G2/M boundary |
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Term
| Why is p53 such an important factor when talking about cancer and DNA damage? |
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Definition
p53 is a transcription factor that acts as a DNA damage sensor; p53 switches on expression of target genes that halt the cell cycle so that DNA can be repaired. If the DNA can't be repaired p53 can initiate apoptosis. Roughly 50% of all human cancers have one or more mutations within the p53 gene |
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Term
| How does MDM2 expression affect p53 and its levels within the nucleus? |
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Definition
The more MDM2 the less p53. MDM2 takes p53 out of the nucleus where it is degraded by the proteasome. DNA damage will initiate the phosphorylation and acetylation of the p53 product |
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Term
| What happens when the DNA damage checkpoint determines that apoptosis is necessary? |
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Definition
A cascade of proteolysis is initiated which culminates in cell death. The proteases involved are called caspases |
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Term
| What happens when Bc12 is overexpressed through something like activation of an oncogene? |
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Definition
Apoptosis, in this case, is blocked and the cell basically becomes immortalized (cancerous) |
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Term
| What happens when Bax and Bc12 production in balanced within cells? |
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Definition
A Bax-Bc12 heterodimer is produced and the cells grow and go through apoptosis like normal |
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Term
| What happens when Bax is overexpressed in cells and more p53 than normal is expressed? |
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Definition
The cells automatically go through apoptosis |
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Term
| What is the primary function of the centrosome duplication checkpoint and how does it accomplish this oversight? |
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Definition
It functions to maintain the normal compliment of chromosomes by monitoring the spindle formation (correlated with cyclin B-CDC2 production) and coordinating with the spindle checkpoint and the exit from mitosis |
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Term
| What is the spindle checkpoint and how does it accomplish its oversight? |
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Definition
The spindle checkpoint monitors the assembly of the spindle and its attachment to the kinetochores. Incorrect or unbalanced attachment to the spindle activates spindle checkpoint proteins which trigger a block in the separation of the sister chromatids by preveting activation of the anaphase-promoting complex (APC/C) |
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Term
| When the correct attachment of chromatids happens in the cells what genes are essentially active and which ones aren't? |
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Definition
CDC20 and APC/C are active but Bub1, 2 and 3 as well as Mad1, 2 and 3 and MPS1 are all inactive |
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