mitosis Flashcards
what is the definition of mitosis?
the division of nuclear genetic material
what is cytokinesis?
the division of the cytoplasm to form two identical daughter cells
what are the stages of the cell cycle?
G1
S
G2
M
what is the G1 phase?
gap phase 1
what is the S stage?
synthesis stage - replication
what is the G2 stage ?
gap phase 2
what is the M phase?
mitosis and cytokinesis
what do K-fibres do?
they also shrink to pull chromatids apart
what happens in the G1 phase?
the cell decides it wants to divide
what happens during the S phase?
the genome is duplicated and chromosomes are replicated to give two sister chromatids
what happens during the G2 phase?
checks occur to ensure there were no mistakes made during chromosome duplication
what happens during the M phase?
mitosis - the division of the nuclear genetic material and transport into the daughter cells
what are the signals for division in the G1 phase?
external and internal
what are external signals for cell division?
growth factors, cell density
what are internal signals for cell division?
sufficient cellular resources
DNA duplicated
absence of DNA damage
what are the stages of the S phase?
chromosomes are duplicated and condensed
the chromosomes are aligned on the equator of the cell
the chromosomes are moved to the daughter cells
what happens during open mitosis?
the nuclear envelope breaks down during division
what happens during closed mitosis?
the nuclear envelope stays intact and division takes place within the envelope
how are chromosomes moved?
mitotic spindle
what are mitotic spindles made of?
microtubule filaments
what are microtubule filaments made of?
alpha and beta tubulin dimers which polymerise to form hollow tubes
how are the mitotic spindles organised?
centrosomes
what do the centrosomes consist of
2 centrioles
what happens to the centrosome during the S phase?
duplicate and divide and form new spindle
what are the three different types of microtubule within spindle?
interpolar
aster
K- fibres
what do interpolar microtubules do?
they stabalise and elongate the spindle during mitosis
what do the aster microtubules do?
stabalise and orientate the spindle at the cell cortex
where do the microtubules attach to the chromosomes?
the centromere
what are kinetocores?
the protein cmplexes that mediate microtubule - DNA attachment
what do the K-fibres do in order to pull the chromatids apart?
shrink
what is the cleavage furrow?
the divide between two daughter cells by a contractile ring
what does the contractile ring consist of ?
actin and myosin
what is the midbody?
the mark left on a divided cell by the contractile ring squeezing the spindle
why can the midbody be important to the cell?
it can be a cell marker
what happens during prophase?
spindle begins to form
aster will for on both sides of the spindle
the interpolar MT will extend to make the spindle longer
the chromosomes will start to condense and the 2 sister chromatids are visible together and attached to each other
what happens during prometaphase?
the nuclear envelope starts to fragment
the mitotic spindle is formed and the Kfibres have attached to the 2 sister chromatids
what happens during metaphase?
the chromosomes are lined along the metaphase plate
what happens during anaphase?
the chromosomes are pulled towards the poles of the cell
what happens during telophase?
the nuclear membrane begins to reform
which enzymes drive the cell cycle?
CDK’s - cyklin dependant kinases
what controls the beginning of M phase?
CDK’s
how do CDK’s work?
they require cyclin to bind to them in order to be activated and carry out phosphorylation. these phosphorylation event can be used as signals to drive the cell cycle.
what are the stages of binary fission within bacterial cells?
chromosome replication begins
one copy of the origin is now attached at each end of the cell
replication finishes
how do bacterial cells know where to divide?
YFP-MinD protein indicates the centre of the cell for the bacteria
