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18 Cards in this Set
- Front
- Back
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What is the role of MPF?
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M-phase promoting factor
Triggers condensation of chromatin Induces assembly of mitotic spindle Separates condensed chromosomes (Cyclin and CDK complex) |
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Name cyclins A to D
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A= cyclin D - regulates progress from G1 to S phase
B= cyclin E - " " C= cyclin A - active in S phase D= cyclin B - regulates progression into M phase |
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How does cyclin B affect levels of MPF?
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Accumulates formation of MPF
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What is MPF activated by?
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Phosphorylation and dephosphorylation events initiated by Wee1, CaK, Cdc25
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What are the stages of mitosis?
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Prophase
Prometaphase Metaphase Anaphase Telophase |
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When does cytokinesis begin/end?
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Begins at anaphase and continues through telophase
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What occurs in prophase and prometaphase?
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Prophase - chromosomes condense, mitotic spindle forms outside nucleus
Prometaphase - nuclear envelope breaks down, sister chromatids attach to spindle |
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What occurs in metaphase and anaphase?
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Metaphase - chromosomes line up on equator and chromatids attach to opposite poles of spindle
Anaphase - chromatids are pulled in opposite directions towards spindle pole |
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What occurs in telophase and cytokinesis?
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Telophase - chromosomes arrive at pole and nuclear envelopes begin to form around both sets
Cytokinesis - contractile ring splits cytoplasm into two cells |
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What must happen to the centrosome before mitosis can occur?
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Centrosomes must be duplicated
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What is the role of the centrosomes?
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They organise microtubules and are required for formation of mitotic spindles
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When does centrosome duplication occur?
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S phase
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What are the 2 roles of Anaphase Promoting Complex? (APC)
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Securin joined to separase
APC targets securin for degradation, separase breaks cohesin links between chromatids APC targets cyclin B for destruction = inactivates MPF and leads to exit from mitosis |
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How are chromosomes pulled apart?
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Kinetochore microtubules are shortened by depolymerisation, loss of tubulin subunits
Separation of spindle poles, interpolar microtubules slide past each other, pulling of astral microtubules |
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What is the contractile ring composed of?
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Actin and myosin filaments
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What is the role of p53?
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Activates cdki p21, which binds to cyclin/cyclindependentkinase complexes and inhibits cell cycle progression
Allows time for repair of damaged DNA |
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How can UV light cause damage to DNA?
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May cause two adjacent bases to bond
e.g. thymine dimer |
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Describe Nucleotide Excision Repair (NER)
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10-20 nucleotides around damaged region cut out but nucleases, repair DNA polymerase makes new correct sequence and DNA ligase seals DNA backbone
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