Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse...
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Transcript of Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse...
Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse individuals
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
Pre- Germ Cell OR Pre-Reproductive Cell
Mother Cell is diploid
2n = 46 BUT in this cartoon version ………
2n= 4
Prophase I
Media Links\13-07b-ProphaseI.mov
#5 ds chromosomes
#9 N.M. gone
#12 Spindle Fibers
#13 Synapsis & Tetrads
#3 Crossing Over
Synapsis - Homologous Pairs of chromosomes come together
Tetrad – 4 homologous chromatids
Media Links\13-10-CrossingOver.mov
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
Telophase I
#1
2 temporary daughter cells are 1n (ds)
Media Links\13-07e-TelophaseICytokin.mov
Cytokinesis occurs
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)
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
Prophase II
#1 1n (ds)
#5 ds chromosomes move to equator
#8 each daughter cell is genetically different
Metaphase II
#1 1n (ds)
#8 each daughter cell is genetically different
#9 chromosomes (ds) align on equator
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
Telophase II
#3 Cytokinesis occurs
#4 Daughter cells are 1n (ss)
#8 Each daughter cell is genetically different
Media Links\13-07f-MeiosisIICytokin.mov
Meiosis II Summary
1. 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