3.2.2 mitosis and cell cycle Flashcards
in which cells does the cell cycle occur?
eukaryotic cells.
what is the order of the cell cycle?
G1 phase > S phase > G2 phase > cell division
what is G1?
growth one, organelle synthesis and protein synthesis.
what is the S phase?
is where DNA replication takes place, where the two chromatids are joined at the centre by a centromere = chromosome.
what is G2?
growth 2.
preparation for mitosis, making cell bigger.
what is the stages of mitosis?
IPMAT:
- interphase.
- prophase.
- metaphase.
- anaphase.
- telophase.
what happens in interphase?
DNA isn’t visible as it is tightly coiled. G1, S and G2 have occurred already.
what happens in prophase?
- nuclear membrane begins to break down.
- DNA condenses = making chromosomes visible.
- spindle fibres start to form between poles of cell.
what happens in metaphase?
- chromosomes line up at the equator of the cell.
- chromosomes attach to spindle fibres by their centromere.
what happens in anaphase?
- centromere breaks.
- chromatids separate and move to opposite poles of the cell.
- the spindle fibres contract to pull chromatids apart.
what happens in telophase?
- nuclear membrane reforms around each mass of chromosomes and spindle fibres break down.
- chromosomes uncoil = no longer visible.
what happens in cytokinesis?
cell membrane and cytoplasm divide to form 2 new cells each containing one nucleus.
how to work out mitotic index?
number of cells undergoing mitosis/total number of cells in field of view
what checks are done at the end of G1?
- cell size.
- DNA damage.
- nutrients.
- are growth factors present?
what checks are done at the end of the S phase?
- is DNA replication complete?
- DNA damage.
= aptosis will occur if cell cannot be repaired.
what checks are done in metaphase?
- are the chromosomes attached correctly to the spindle fibres?
what can happen if the cell cycle and cell division is uncontrolled?
cancer.
what checkpoint genes stops the cycle when damage is detected?
tumour suppressor genes = disabled and switched off if cancer is present.
what stimulates cell division?
proto-oncogenes = switched on and increased in activity when cancer is present.
how is cancer treated?
- sometimes involves the blocking of parts of the cell cycle = so cell division and cancer growth stops, disrupting all the cells in the body, mostly rapidly growing cells like hair follicles = common side effect of cancer.
