Mitosis Flashcards
What is mitosis?
The division of the cell (the nucleus), producing 2 genetically identical daughter cells
Daughter cells are identical to parent cell + contain same num of chromosomes
What is mitosis used for?
- Growth
- Replacement + repair of tissues in multicellular organisms
- Asexual reproduction (in some unicellular + multicellular organisms)
What are examples of multicellular organisms?
Animals, plants, fungi
What are the 4 stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telephase
How are the stages of mitosis described?
Distinct, but flow seamlessly from 1 to the other
How can each stage be identified?
Using a light microscope - based on characteristic features of chromosomes as they move
Where are dividing plant cells easily found?
In root tips of plants, part of meristems (actively dividing regions of plants)
How can the DNA within cells be seen?
Using staining - usually methylene blue
What happens in prophase (part 2)?
- 2 Centrioles migrate to opposite parts of cell
- Spindle fibres attack to specific parts on centromere + move chromosomes to centre of cell
- Nuclear envelope disappears
What happens in prophase (part 1 - creating chromosomes)?
- Chromatin fibres coil + condense to form chromosomes (that take up staining). Nucleolus disappears, nuclear membrane starts breaking down
- Protein microtubules form spindle-shaped structures, linking poles of cell
What happens during the metaphase?
Chromosomes moved by spindle fibres to form plane in centre of cell (called metaphase plate), then held in position
Explain the anaphase:
- Centromeres holding together chromatids divide, separating them to opposite poles of cell
- Characteristic “V” shape of chromatids moving towards poles is result of them being dragged by centromeres through liquid cytosol
What happens during the telophase?
- Chromatids have reached poles, now called chromosomes
- 2 new sets of chromosomes for, at each pole + nuclear envelope reforms around them
- Chromosomes uncoil + nucleolus formed
- Cell division/cytokinesis begins
What happens during cytokinesis in animal cells?
- Cleavage furrow forms around middle of cell
- Cell-surface membrane pulled inward by cytoskeleton until its close enough to fuse around middle, making 2 cells
Why cant a cleavage furrow be formed during cytokinesis in plant cells?
They have a cell wall