1.6: Cell division. Mitosis Defined as: division of a nucleus into two genetically identical...
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Transcript of 1.6: Cell division. Mitosis Defined as: division of a nucleus into two genetically identical...
![Page 1: 1.6: Cell division. Mitosis Defined as: division of a nucleus into two genetically identical daughter nuclei. When does mitosis occur? 1. Growth (incl.](https://reader035.fdocuments.in/reader035/viewer/2022062516/56649e355503460f94b23af7/html5/thumbnails/1.jpg)
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1.6: Cell division
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Mitosis
Defined as: division of a nucleus into two genetically identical daughter nuclei.
When does mitosis occur?
1. Growth (incl. embryonic development)
2. Repair
3. Asexual reproduction
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IP
MA
TCtelophase
interphase
metaphase
anaphase
prophase
cytokenesis
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Before…DNA is replicated, cell makes a complete copy of it’s genetic material (Interphase).
Each chromatid has an identical copy (sister chromatid)
Sister chromatids are attached at the centromere
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Prophase
Chromosome become visible – shorter & coil
Homologous chromosomes (homologues) pair up – maternal & paternal chromosomes are side by side (their formation is known as synapsis)
Spindle fibers made from microtubules form.
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MetaphaseBivalents (paired homologous chromosomes) line up along equator
Nuclear membrane disappears
Spindle attaches to centromere
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Anaphase
Spindle fibers from poles attach to chromosomes
Spindle fibers pull chromosomes to the poles of the cell
Sister chromatids separate.
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TelophaseSpindles & spindle fibers disintegrate
Chromosomes uncoil
Nuclear membrane forms
Two genetically identical daughter cells are formed.
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Task: Make a mitosis ‘flip book’ detailing the stages of mitotic division. Notes available on pg. 53/54.
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The mitotic index
Using a micrograph to estimate the ration between the number of cells in mitosis and the total number of observed cells.
Mitotic index = number of cells in mitosis
total number of cells
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Cytokinesis
Is different in plants and animals.
Plants Animals
Vesicles move to the equator, fusing together forming a double plasma membrane layer across the cell.
Pectin & other substances are moved between this new layer, combining with cellulose to eventually form a new cell wall.
Plasma membrane pulled inwards
Proteins actin & myosin contract the plasma membrane, pinching the cell into two.
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The Cell Cycle
Regulated by cyclins (proteins).
Cyclins bind to enzymes called cyclin-dependent kinases
Active kinase attach phosphate groups to other proteins which triggers more proteins to become active.
In humans there are four types of cyclin. See fig. 6, pg. 56
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Tumours & cancer
Read detail on pg. 57, including the correlation between smoking and cancer.
Data based qu. Pg. 59.