The Cell Cycle & Its Control Flashcards

Question

What happens during telophase?

Answer 1

* Daughter chromsomes arrive at spindle * Nuclear envelope reassembles at each pole • Contractile ring forms - made up of actin & myosin

Answer 2

The contractile ring forms | • it contracts, leaving behind a mid-body

Answer 3

Transition out of metaphase - monitors: • chromosome alignment AND • the spindle assembly HENCE monitors kinetochore activity • an unattached kinetochore generates a checkpoint signal = will NOT let system advance into anaphase

Answer 4

CENP-E BUB protein kinases • these dissociate from the kinetochore when the chromosome properly attaches to the spindle (when all dissociated, anaphase proceeds)

Answer 5

(a) mis-attachment of microtubules to kinetochores (b) aberrant centrosome/DNA duplication

Answer 6

Amphelic • normal Monotelic • only ONE kinetochore bound Merotelic • BOTH centrosomes to same kinetochores • sister chromosome lost during cytokinesis Syntelic • same centrosome to both kinetochores • will put BOTH sister chromosomes to one side (ONENOTE for picture!!)

Answer 7

DNA and centrosome duplication ``` • leads to too many centrosomes (often 4) AND • a multipolar spindle = • aberrant cytokinesis ```

Answer 8

Induces gross chromosome mis-segregations Inhibits attachment • error-correction mechanism

Answer 9

Chekpoint kinase (CHKE1 & CHKE2) * serine theronine kinase activation holds cells in G2 phase until all is ready * inhibition leads to untimely cell transition to mitosis

Answer 10

Taxanes & vinca alkaloids • alters microtubule dynamics • produces unattached kinetochores • causes long-term mitotic arrest

Answer 11

1. Cell Cycle ARREST • at check points (G1 & spindle check) • can be temporary (i.e. following DNA repair) 2. APOPTOSIS • DNA damage too great so cannot be repaired • Chromosomal abnormalities • Toxic agents

Answer 12

1. During G1 • GFs required to exit G0 and into G1 2. BEFORE mitosis (G2 checkpoint) • to check for DNA damage 3. Metaphase checkpoint • check for sister chromatid alignment

Answer 13

In the absence of stimulus: • cells go into the G0 stage (quiescent phase) • cells are NOT dormant but are NON-dividing Exit from G0 is highly regulated • requires GFs & IC signalling cascades

Answer 14

Tumours ignore ALL the checkpoints ALSO Tumours block the ability of the cell to exit the cycle into G0 • thus cell CONTINUES to DIVIDE

Answer 15

* Response to EC factors * Signal amplification * Signal integration * Modulation (via. other pathways) * Regulation of divergent responses (look at ONENOTE picture!!)

Answer 16

Ligand binds and activates the receptor! e.g. EGF (epidermal) & PDGF (platelet-derived) Receptors are MONOMERIC in their INACTIVE state - when ligand binds • receptors form dimers = kinase cascade • kinases are PHOSPHOSRYLATED = binding of adapted proteins

Answer 17

``` • Phosphate transfer from ATP - to a hydroxyl group - examples of side chains that can be phosphorylated include • serine • THREONINE • tyrosine ``` The added phosphate can alter the protein function by: • change in conformation --> change in activity • creating a docking site for another protein

Answer 18

In presence of ligands (a) receptors form dimers (b) are activated by phosphorylation Receptor activation triggers: (a) kinase cascades (b) binding of adapted proteins

Answer 19

Normally, the protein regulated by a kinase is ANOTHER kinase (and so on)...... i.e. activation of one kinase activates another to activate another This leads to • signal amplification • signal diversification • opportunity for regulation

Answer 20

Phosphates