Mitosis Flashcards
What are the stages of mitosis?
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What is interphase?
DNA isn’t visible as tightly coiled - allows access to genes for transcription
What happens during Prophase?
Chromosomes condense and become visible
appear as chromatids joined at centromere
What happens in metaphase?
Chromosomes line up at equator and attach to spindle fibres by centromere
What happens during anaphase?
Chromatids separate and centromere splits as spindle fibres pull chromatids to opposite poles of cell
What happens in telophase?
Chromosomes uncoil and become no longer visible
Nuclear membrane reforms around each mass of chromosomes
What is cytokinesis?
Cell membrane + cytoplasm divides to form two new cells - each containing 1 nucleus
What is mitotic index?
number of cells containing visible chromosomes in field of view
divided by
total number of cells in the field of view
What is the cell cycle?
Growth 1 - organelle synthesis
S phase - DNA replication
Growth 2 - more organelle synthesis (prepare for mitosis)
Mitosis phase - cell division
How is the cell cycle controlled?
3 checkpoints checking for:
DNA damage
Incomplete DNA replication
Big enough cell
Will chromatids split
Where is first checkpoint?
end of growth 1
checks for:
cell size
DNA damage
sufficient nutrients
are growth factors present
Where is the 2nd checkpoint?
end of s phase
checks for:
DNA replication
DNA damage
Where is the 3rd checkpoint?
metaphase
checks that:
chromosomes have attached correctly to spindle fibres
What happens if cell doesn’t pass checks?
repair: cell cycle continues
repair not possible: apoptosis (cell destroyed)
What is cancer?
uncontrolled cell division
What causes cancer?
tumour suppressor gene switched off/disabled
or
proto-oncogenes switched on / increased activity
(stimulate cell division)
What are the features of cancer cells?
divide even when growth factors missing
divide more readily than healthy cells
How to treat cancer?
blocking some part of cell cycle
disrupting cell cycle - cell division
What is the problem of cancer treatment?
disrupts all cells in body
- hair loss = cells in hair follicles divide more readily so more affected by chemotherapy
