Mitosis and Cytokinesis Flashcards
What are phases regulated by?
Cyclin-dependant kinases (Cdks). Cdks phosphorylate target proteins to activate the next stage
Prophase
Chromosomes condense and become visible. Spindle fibers emerge from the centrosomes. Nuclear envelope breaks down. Nucleolus disappears.
Prometaphase
Chromosomes continue to condense. Kinetochores appear at the centromeres. Mitotic spindle microtubules attach to to kinetochores. Centrosomes move toward opposite poles.
Metaphase
Mitotic spindle is fully developed, centrosomes are at opposite poles of the cell. Chromosomes are lined up at the metaphase plate. Each sister chromatid is attached to a spindle fiber originating from opposite poles.
Anaphase
Cohesin proteins binding the sister chromatids together break down. Sister chromatids (now called chromosomes) are pulled towards opposite poles.
Non-kinetochore spindle fibers lengthen, elongating the cell.
Telophase
Chromosomes arrive at opposite poles and begin to decondense. Nuclear envelope material surrounds each set of chromosomes. The mitotic spindle breaks down.
Cytokinesis in Animal cells
a cleavage furrow separates the daughter cells
Cytokinesis in Plants
a cell plate separates the daughter cells
Kinetochores
appear during metaphase. Are protein sequences that ‘hang out’ around centromere
Sister Chromatids kept together by
Kept together by cohesin (protein complex)
Cohesin proteins break down in…
Anaphase
Spindle Fibres
Compromised of microtubules (hollow tubes of tubulin). Move chromosomes via addition and deletion of tubulin subunits and motor proteins. Motor proteins cause non kinetochore microtubules to walk along each other and push poles apart. Pole separation achieved by addition of tubulin to polar (non-kinetochore) microtubules
