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Meiosis (Period 1 Group 1)

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Jennifer Wong

on 6 December 2014

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Transcript of Meiosis (Period 1 Group 1)

Meiosis Cookies
1. 15 Store-bought Sugar Cookies
2. 1 Jar of Icing (Betty Crocker)
3. Food coloring
5. Ziploc bags
6. 4 Small cups & spoons
7. Scissors
8. Tray or paper plates
9. Parchment paper
Question #1:
What changes during meiosis? What is the significance of these changes? Why is variation important?
Question #2:
What is crossing over? When does it occur? What is its significance?
Final Result!
1. Put in a sufficient amount of icing into 4 cups.
2. Put in 2-3 drops of food coloring (different colors for each cup) & mix.
3. Put the icing in one corner of the Ziploc bag & make sure that it's in tight (no spaces or air bubbles). Then cut a small hole in the corner of the bag.
4. Lay out 15 cookies on a tray.
5. Make sure that 6 of the cookies are next to each other to represent the Telophases (I & II) & Cytokineses.
6. Use the
icing for the Mom chromosome & use the
icing for the Dad chromosome.
7. Use the
icing for the Centrioles & the spindles.
8. Use the
icing for the fragments of nuclear envelope.
By: Sharon Kao, Shereen Lam, Nicole Sam, Bonnie Tran, Jennifer Wong
Period 1

Question #3:
Meiosis 1
Meiosis 2
Prophase 1:
Metaphase 1:
Anaphase 1:
Telophase 1:
Prophase 2:
Metaphase 2:
Anaphase 2:
Telophase 2:
Chromatin are dispersed & not condensed
Homologous chromosomes duplicates (like Mitosis)
1 X = sister chromatids
2 X = homologous chromosomes
Nucleolus & nuclear envelope is intact
Nucleolus disappears & Nuclear envelope breaks down (fragments)
Chromosomes become visible under a microscope as a tetrad
Tetrad: a group of 4 chromosomes
Crossing over
: Mom & Dad chromosome (homologous pairs) switch parts of their chromosome; DNA breaks & reattach
: Chromosome pairs become connected by a zipper-like protein structure
Spindle forms between 2 pairs of centrioles as they move to opposite poles
Tetrad is separated/pulled apart by the spindles
Are now sistar chromatids
Move towards opposite sides of cell
Sistar chromatids are still attached (Still an X)
In Meiosis, sister chromatids are still attached together
In Mitosis, sister chromatids are separated
Mom chromosome has a piece of the Dad chromosome
Dad chromosome has a piece of the Mom chromosome
Prophase 1
Centrioles are at opposite poles of the cell
Mom & Dad chromosomes line up in the middle of the cell (metaphase plate)
Still crossed over
One chromosome in each pair face each pole
Spindle fibers attach to homologous chromosomes
Metaphase 1
Anaphase 1
Chromosomes finish making their way to the 2 poles
Chromosomes still consist of 2 sister chromatids
One region will consist of nonsister chromatid DNA
Nuclear envelope reforms around each chromosome set
Spindle disappears
Cleavage furrow
Chromosomes still composed of 2 chromatids
Nuclear envelope breaks down
Spindle forms
2 chromatids of each chromosome move to opposite poles as individual chromosomes
No longer sister chromatids (not an X)
Nuclear envelope forms around each set of chromosomes
Chromosomes are decondensed & spindles disappear
4 daughter cells are produced (gametes)
Daughter cells are genetically distinct from one another & from parent cell
Cell is split to 2
2 haploid daughter cells
No more chromosome duplication after this
Telophase 1 & Cytokinesis
Chromosomes line up on metaphase plate
Because of crossing over in Meiosis 1, the 2 sister chromatids are not genetically identical
Spindle attach to chromosomes at opposite poles
What is the end product of Meiosis 1 and Meiosis 2?
Fill in the key parts of each phase in the table.
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