Meiosis is used in sexual reproduction to make genetically diverse gametes genetically diverse individuals.

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

Interphase

Pre-Reproductive Cell#8 M.C. is 2n#10 Nucleolus

#2 duplication

Prophase I

Media Links\13-07b-ProphaseI.mov

#5 ds chromosomes

#9 N.M. gone

#12 Spindle Fibers

#13 Synapsis & Tetrads

#3 Crossing Over

Prophase I

Sister

Chromatids

Non-Sister

Chromatids

Synapsis - Homologous Pairs of chromosomes come together

Tetrad – 4 homologous chromatids

Media Links\13-10-CrossingOver.mov

Metaphase I

#6

Homologous pairs of chromosomes align on equator

Media Links\13-07c-MetaphaseI.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

Gametes

#4

#8

#4 Daughter cells are 1n (ss)

#8 Each daughter cell is genetically different

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

And Now It Is Time To Start The Meiosis Lab...

Grab your Chromosomes Cups and begin!!!!!