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26 Cards in this Set
- Front
- Back
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In which phase of the cell cycle does DNA replication take place?
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S-Phase
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Which phase of the cell cycle determines the length of the cycle?
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G1-Phase
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What occurs in the gap phases of the cell cycle?
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Growth in size and doubling of proteins and organelles
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Which part of the cell cycle is growth factor dependent? Growth factor independent?
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Dependent: early G1-Phase
Independent: late G1-Phase & S phase |
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Cell cycle control is similar in all eukaryotes. T/F?
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True
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Cyclins serve as the __________, while Cdk's serve as the ____________ in the Cyclin-Cdk complex.
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regulatory subunits, catalytic subunits
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How many catalytic subunits do yeasts have?
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only Cdk-1 which can bind to various regulatory subunits(cyclins)
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What are the components of G1-Cdk complex in eukaryotes?
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Regulatory: Cyclin D
Catalytic: Cdk4, Cdk6 |
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When is Cdk active?
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Its partially active when its associated with cylcin and fully active after phosphorylation by CAK.
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Why are the regulatory subunits called cylcins?
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Their level of expression changes during the cell cycle.
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Does the expression of the catalyitic subunits change durging the cell cycle? how about regulatory?
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No, It remains constant. However, the regulatory subunit changes in expression.
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When does cyclin B peak in terms of expression?
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M-phase
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What is CAK?
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Cdk-Activating kinase, it fully activates the cyclin-cdk complex by adding a phosphate group.
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How can G1-Cdk complex be specifically inhibited?
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P16 INK4A
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How do Cdk inhibitor proteins (CKIs) work?
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1. They can work by binding to the cyclin-cdk complex, thus blocking the activity of the complex.
2. They can also work by binding to the catalytic subunit(cdk) and preventing it from interacting with the regulatory subunit(cyclin).[competitive inhibition] |
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What is the purpose of RB protein?
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It is an important regulator of the transition from G1 to S-phase. Which is the time of commitment to DNA synthesis or passage through the restriction pt.
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When is RB protein active? How is it inactivated?
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When its not phosphorylated. Its inactivated upon phosphyrlation by the cyclin-cdk complex.
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How does RB regulate the cell cycle?
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It binds to E2F preventing its action (which is to regulate transcription of genes). Ultimatley preventing entry into S-Phase or DNA synthesis.
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In quiescent cells what is the status of RB?
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RB is active
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Which substrate is involved in the G2-M transition of the cell cycle?
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Seperase which promotes seperation of chromatids (Metaphase to Anaphase)
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In regards to the cell cycle what is a checkpoint and where are they located.
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Checkpoints control DNA synthesis occurs properly without damaged DNA.
G1-S check pt: makes sure DNA isnt damaged. G2-M check pt: if damaged DNA makes it through and gets duplicated this check pt blocks cell division. |
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How is P53 activated?
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It is activated when DNA is Damaged. i.e. double strand breaks via radiation
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what happens after P53 gets activated?
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P53 activates P21 which is a cdk inhibitor protein. Which in turn deactivates the cyclin-cdk complex of the G1 and S phases. The end result is cell cylce arrest, this allows the DNA to make the necessary repairs.
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what is the action of chk1/2 (checkpoint kinase)?
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Cell arrest at G2-M phase. Prevents duplication of damaged DNA.
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How does the Myc gene effect the cell cylce?
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1. Increase cyclin D
2. Increase P27 Degredation 3. Increased E2F synthesis all are stimulatory mechanisms and lead to entry into the S-Phase. |
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What is one extracellular growth inhibitory molecule? which part of the cell cycle does it effect?
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TGF-B effects G1-S transition (stops it)
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