Protein control of cell division Flashcards
What is the cytoskeleton?
A complex network of protein filaments that give mechanical support and shape to cells.
What does the cytoskeleton consist of?
The cytoskeleton consists of different protein structures including microtubules which are found in all eukaryotic cells.
What do microtubules control?
Microtubules control the movement of membrane-bound organelles and chromosomes.
What does cell division require?
Cell division requires remodelling of the cytoskeleton.
What involves polymerisation and depolymerisation of tubulin?
Formation and breakdown of microtubules involves polymerisation and depolymerisaton of tubulin.
What forms spindle fibres that are active during cell division?
Microtubules form the spindle fibres that are active during cell division.
What does the cell cycle consist of?
The cell cycle consists of interphase and the mitotic (M) phase.
What does the mitotic phase involve?
The mitotic phase involves mitosis and cytokinesis.
What does mitosis consist of?
Mitosis consists of prophase, metaphase, anaphase and telophase.
What happens at G1?
Growth phase
What happens at S?
Its the phase where DNA is replicated
What happens at G2?
Growth phase
What happens at Prophase?
DNA condenses into chromosomes each consisting of two sister chromotids. Nuclear membrane breaks down, spindle microtubules extend from the MTOC by polymerisation and attach to chromosomes via their kinetochores in the centromere region.
What happens at metaphase?
Chromosomes are aligned at the metaphase plate (equator of the spindle)
What happens at anaphase?
As spindle microtubules shorten by depolymerisation, sister chromatids are separated and the chromosomes are pulled to opposite poles.
What happens at telophase?
The chromosomes decondense and nuclear membranes are formed around them.
How is progression through the cell cycle controlled?
Progression through the cell cycle is controlled by checkpoints.
What is involved in regulationg the cell cycle?
Cyclin proteins that accumlate during cell growth are involved in regulating the cell cycle.
What happens at the G1 checkpoint?
At the G1 checkpoint, retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcripton of genes that code for proteins needed for DNA replication.
How does phosphorylation inhibit the retinoblastoma protein?
Phosphorylation by G1 cyclin-CDH inhibits the retinoblastoma protein (Rb)
What happens at the G2 checkpoint?
At the G2 checkpoint, the success of DNA replication and any damage to DNA is assessed.
What does DNA damage trigger?
DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death.
What does the metaphase checkpoint control?
The metaphase checkpoint controls progression from metaphase to anaphase.
What may result in degenerative diseases?
An uncontrolled reduction in the rate of cell cycle may result in degenerative disease.
What may result in tumour formation?
An uncontrolled increase in the rate of the cell cycle may result in tumour formation.
Is a proto-oncogene a normal gene?
A proto-oncogene is a normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene
What is apoptosis triggered by?
Apoptosis is triggered by cell death signals that can be external or internal.
What do external death signals do?
External death signal molecules bind to a surface receptor protein and trigger a protein cascade within the cytoplasm.
What do internal death signals result from?
An internal death signal results from DNA damage which causes activation of p53 tumour-suppressor protein.
Why is apoptosis essential?
Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis.
What happens in the absense of growth factors?
Cells may initiate apoptosis in the absence of growth factors
