Protein control of cell division Flashcards
what is the function cytoskeleton
The cytoskeleton gives mechanical support
and shape to cells
what does the cytoskeleton consist of
It consists of different protein structures including microtubules, which are found in all eukaryotic cells
what are micro-tubules
Microtubules are hollow cylinders composed
of the protein tubulin. They radiate from the
microtubule organising centre (MTOC) or
centrosome.
what do the microtubules controls
Microtubules control the movement of
membrane-bound organelles and
chromosomes
what does cell division require
Cell division requires remodelling of the
cytoskeleton
what does the Formation and breakdown of microtubules
involve
Formation and breakdown of microtubules
involves polymerisation and depolymerisation
of tubulin
what do micro tubules form
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
mitotic (M) phase
what does the mitoic phase invovle
Mitotic phase involves mitosis and
cytokinesis
what does inter phase involve
Interphase involves growth and DNA
synthesis including G1, a growth phase; S
phase, during which the DNA is replicated;
and G2, a further growth phase.
In mitosis what is the chromosomal material separated by
In mitosis the chromosomal material is separated by the spindle microtubules. This
is followed by cytokinesis, in which thecytoplasm is separated into two daughter
cells.
what does mitosis consist of
Mitosis consists of prophase, metaphase,
anaphase and telophase
what happens in prophase
Prophase — DNA condenses into chromosomes each consisting of two sister
chromatids. 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 during metaphase
Metaphase — chromosomes are aligned at
the metaphase plate (equator of the spindle).
what happens during anaphase
Anaphase — as spindle microtubules shorten
by depolymerisation, sister chromatids are
separated, and the chromosomes are pulled
to opposite poles
what happens during telophase
Telophase — the chromosomes decondense
and nuclear membranes are formed around
them.
what is progression through the cell cycle controlled by
Progression through the cell cycle is controlled by checkpoints
what are checkpoints
Checkpoints are mechanisms within the cell
that assess the condition of the cell during
the cell cycle and halt progression to the next
phase until certain requirements are met.
what are cyclin proteins that accumulate during cell growth involved in
Cyclin proteins that accumulate during cell
growth are involved in regulating the cell
cycle
Cyclins combine with and activate cyclindependent kinases (CDKs). Active cyclinCDK complexes do what
Cyclins combine with and activate cyclindependent kinases (CDKs). Active cyclinCDK complexes phosphorylate proteins that
regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs.
what happens at the G1 checkpoint
At the G1 checkpoint, retinoblastoma protein
(Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication
wshat does phosporylation by G1 cylclin-CDK inhibit
Phosphorylation by G1 cyclin-CDK 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
This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase
DNA damage triggers the activation of several proteins including what
DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or
cause cell death
what doe a metaphase checkpoint control
A metaphase checkpoint controls progression from metaphase to anaphase
at the metaphase checkpoint what happens
At the metaphase checkpoint, progression is
halted until the chromosomes are aligned
correctly on the metaphase plate and attached to the spindle microtubules.
An uncontrolled reduction in the rate of the cell cycle may result in what?
An uncontrolled reduction in the rate of the cell cycle may result in degenerative disease
An uncontrolled increase in the rate of the cell cycle may result in what?
An uncontrolled increase in the rate of the cell cycle may result in tumour formation
What is a proto-oncogene
A proto-oncogene is a normal gene, usually
involved in the control of cell growth or division, which can mutate to form a tumourpromoting oncogene
what is apoptosis triggered by
Apoptosis is triggered by cell death signals that can be external or internal
The production of death signal molecules from lymphocytes is an example of what
The production of death signal molecules from lymphocytes is an example of an external death signal. DNA damage is an
example of an internal death signal.
External death signal molecules bind to a
surface receptor protein and trigger what
External death signal molecules bind to a
surface receptor protein and trigger a protein
cascade within the cytoplasm
what does an internal death signal resulting from DNA damage cause
An internal death signal resulting from DNA
damage causes activation of p53 tumoursuppressor protein
What do both types of death signal result in what?
Both types of death signal result in the activation of caspases (types of protease
enzyme) that cause the destruction of the cell
apoptosis is essential during what?
Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis
cells may initiate apoptosis in absence of what?
Cells may initiate apoptosis in the absence of growth factors
