Mitosis and cell cycle control W5 Flashcards
Varying lengths of cell cycles
Embryonic cells may take two hours
Cells in an adult may take 20 to 24 hours
How long is interphase?
20 to 22 hours
How long is the mitotic phase?
Typically one to 2 hours
Interphase G1
Cells are metabolically active + increase in size
Synthesise proteins and produces organelles
Prepare prepared for DNA replication by gathering energy
Checks it environment to see if the conditions are correct to keep dividing
(Basically it is like the sale getting everything ready before it copies it it’s DNA in the next phase)
S stage
Every chromosome is duplicated
The copies stay attached together at the centromere forming sister chromatids
Also grow a little
Interphase G2
Keeps growing and makes more proteins and organelese
Repairs any DNA errors from S phase
(Basically the final double check before teh cells splits)
Mitosis requires what?
Microtubules
They act like ropes that help move and separate the chromosomes
Three classes of Spindle microtubule
Kinetochore microtubules - grab chromosomes
Polar microtubules - push poles apart
Astral microtubules - anchor the spindle
Microtubule motor proteins
- Kinesins : walk towards the positive end of a microtubule
- Dyneins : move towards the microtubules negative end.
Mitotic machinery
the set of structures and proteins the cell uses to divide chromosomes during mitosis.
It includes:
- Spindle fibers
- Centrosomes
- motor proteins
Five stages of mitosis
- Prophase.
- Prometaphase
- Metaphase.
- Anaphase.
- Telophase
- Cytokinesis.
- Prophase.
Chromosomes condense and become visible.
The nuclear envelope starts to break down.
The spindle fibers begin to form from centrosomes.
- Prometaphase
nuclear envelope completely disappears.
Spindle fibers attach to chromosomes at the kinetochore.
Chromosomes start moving around, getting ready to line up.
- Metaphase.
Chromosomes line up neatly in the middle of the cell
All chromosomes are attached to spindle fibers from both sides.
- Anaphase.
Sister chromatids are pulled apart by the spindle fibers.
Each set moves toward opposite ends (poles) of the cell.
- Telophase
Chromosomes arrive at opposite poles.
New nuclear envelopes form around each set of chromosomes.
Chromosomes start to unwind back into loose DNA.
The cell is almost ready to split.
- Cytokinesis.
cell fully splits into two!
The cytoplasm is divided by contractile ring
Each daughter cell will receive its complement of organelles
The contractile ring
cytoskeletal structure responsible for cytokinesis
Consists mainly of actin and myosin filaments
It is arranged in a ring around the equator of the cell
It starts to assemble beneath the plasma membrane at the end of mitosis
As the ring contracts, it pulls the membrane inwards, dividing the cell into
It disassembles completely once the cell is divided in to
How do cells controlled their proliferation?
Like traffic lights
Checkpoints: G1, G2 and M
Growth factors
Timor suppressor genes
Cycling’s and CDKs
How to sell control the activity of their proteinsn
Phosphorylationon - adding phosphate group to a protein to turn it off or on
Proteolysis - breakig down proteins when they are no longer needed
Controlling how much protein is made
True or false? Both phosphorylation and dephosphorylation can activate or deactivate the protein depending on where the phosphate is added or removed?
T
Adding and removing a phosphate both activate or deactivate a protein 
True or false? Inhibitory proteins inhibit the function/activity of other proteins that they bind to?
T
They bind to other proteins and block their function/activity
Q. Protein activity can be altered by:
a) Making new protein
b) Targeting protein for degradation
c) Binding to inhibitory proteins
d) All of the above
D
Cyclins
On their own, they are not active
Need to find to CDKs to become active (cyclin is the key and CDK is the engine- without the key the engine can’t start)
They are proteins that control the timing of the cell cycle
Different cyclins are expressed at different parts of the cell cycle
They activate CDKs
