Term
| What are the two main phases of the cell cycle? |
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Definition
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Term
| What are the 3 stages of interphase? |
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Definition
Gap 1: normal cellular activities
S: DNA replication & increase synthesis of histones
Gap 2: growth & preparation for mitosis |
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Term
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Definition
| When a cell becomes arrested in G1. |
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Term
| What occurs during prophase? |
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Definition
-chromosomes condense
-mitotic spindles form
-nuclear envelope breaks down |
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Term
True or False
The breakdown of nuclear membranes, nuclear lamina and NPC is a reversible process |
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Definition
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Term
| What are the stages of M phase? |
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Definition
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis |
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Term
| How is progression through the cell cycle regulated? |
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Definition
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Term
| What are the primary checkpoints in the cell cycle? |
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Definition
end of G1: cell commits to DNA replication in S
end of G2: cell commits to M phase
end of M: cell commits to chromosome segregation |
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Term
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Definition
| cyclin-dependent kinases which phosphorylate target proteins to turn them on or off |
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Term
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Definition
| proteins which vary in concentration, binding to Cdks to change their conformation & regulate their activity |
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Term
| What regulates Cdk activity? |
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Definition
| changes in the concentration levels of cyclins |
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Term
| Is there a high or low concentration of cyclin during G1? |
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Definition
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Term
| Is there Is there a high or low concentration of cyclin at the end of G2? |
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Definition
high
-cell will enter M phase |
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Term
| What are some examples of proteins that Cdks might target for phosphorylation? |
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Definition
histones - for chromatin packing
condensins - for chromosome condensation
lamins - disassembly of nuclear lamina
NUPs - disassembly of the NPC |
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Term
| What happens to soluble nuclear proteins when the nucleus disassembles in prophase? |
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Definition
| they are released into the cytosol |
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Term
| During reformation of the nuclear lamina, envelope & NPC, will Cdk activity be high or low? |
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Definition
| low, NUPs & lamins need to dephosphorylate |
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Term
True or False
Different cyclins can bind to the same cyclin-dependent kinase |
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Definition
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Term
True or False
Cyclins have a nuclear localisation signal and a nuclear export signal |
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Definition
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Term
| What causes a cyclin to be localized primarily to the nucleus or the cytosol depending on where it is needed? |
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Definition
| Phosphorylation of the NLS or NES depending on what phase the cell is in |
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Term
| Up to and during G2, what will be more active, the NES or NLS of a cyclin B1? |
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Definition
NES
cyclin is localized mostly to cytosol |
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Term
| At the end of G2, what will be more active, the NES or NLS of a cyclin B1? |
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Definition
NLS
cyclin is localized to the nucleus |
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Term
| What are the 5 mechanisms of Cdk regulation? |
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Definition
-cyclin binding to activate Cdk
-proteolysis of cyclins
-phosphorylation state of Cdk
-Cdk inhibitors
-subcellular localization of cyclins |
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Term
| What happens when cyclins are ubiquitylated? |
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Definition
| They will be targeted to proteasomes for degradation, Cdks won't be activated |
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Term
True or False
Ubiquitylation of cyclins is irreversible |
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Definition
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Term
| If a Cdk-mitotic cyclin complex is phosphorylated, will it be active or inactive? |
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Definition
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Term
| What do Cdk inhibitors do? |
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Definition
| bind to Cdk to prevent formation of a Cdk-cyclin complex |
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Term
| Where does mitotic cyclin B1 need to be in order to initiate mitosis? |
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Definition
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