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Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse individuals
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MEIOSIS
The production of eggs and sperm
The “Reduction Division ”
Mother Cell (2n) Gamete (1n)
Starts with 46 Ends with 23
Media Links\13_08Meiosis.mpg
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Pre- Germ Cell OR Pre-Reproductive Cell
Mother Cell is diploid
2n = 46 BUT in this cartoon version ………
2n= 4
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Interphase
Pre-Reproductive Cell#8 M.C. is 2n#10 Nucleolus
#2 duplication
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Prophase I
Media Links\13-07b-ProphaseI.mov
#5 ds chromosomes
#9 N.M. gone
#12 Spindle Fibers
#13 Synapsis & Tetrads
#3 Crossing Over
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Prophase I
Sister
Chromatids
Non-Sister
Chromatids
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Synapsis - Homologous Pairs of chromosomes come together
Tetrad – 4 homologous chromatids
Media Links\13-10-CrossingOver.mov
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Metaphase I
#6 Homologous pairs of chromosomes align on equator
Media Links\13-07c-MetaphaseI.mov
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Anaphase I#7 Homologous pairs of chromosomes separate and are pulled to poles #11 ½ of homologous pair is at 1 pole, the other ½ is at the other pole
Media Links\13-07d-AnaphaseI.mov
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Telophase I
#1 2 temporary daughter cells are 1n (ds)
Media Links\13-07e-TelophaseICytokin.mov
Cytokinesis occurs
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Meiosis I Summary
1. Crossing Over Occurred
(Ensures Genetic Variation)
2. Separated the
Homologous Pair of Chromosomes
Cell went from 2N to 1N (ds)
3. Started as 2N = 46 (ds), ended as
N = 23 (ds)
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Interkinesis – Meiosis Intermission
Are these cells 1N or 2N?
#1 Both cells are 1n (ds)
#6 Intermission of Meiosis
#8 Each daughter cell is genetically different
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Prophase II
#1 1n (ds)
#5 ds chromosomes move to equator
#8 each daughter cell is genetically different
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Metaphase II
#1 1n (ds)
#8 each daughter cell is genetically different
#9 chromosomes (ds) align on equator
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Anaphase II
#2 Centromeres break
#7 (ss) chromosomes are pulled to poles
#4 (future) Daughter cells will be are 1n (ss)
#8 each daughter cell is genetically different
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Telophase II
#3 Cytokinesis occurs
#4 Daughter cells are 1n (ss)
#8 Each daughter cell is genetically different
Media Links\13-07f-MeiosisIICytokin.mov
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Gametes
#4
#8
#4 Daughter cells are 1n (ss)
#8 Each daughter cell is genetically different
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Meiosis II Summary1. Separated the chromatids,
Centromeres broke
2. 2 temporary daughter cells went from
Haploid (ds) to Haploid (ss)
3. Started as n = 23 (ds) ended as
n = 23 (ss)
Media Links\13_08Meiosis.mpg
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And Now It Is Time To Start The Meiosis Lab...
Grab your Chromosomes Cups and begin!!!!!
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