Day 3 ­ Notes and Activity.notebook
February 13, 2014
Unit 2B ­ Meiosis
Day 3 ­ Stages of Meiosis Learning Goal: • Know the correct order of the stages in meiosis.
• Understand key vocab terms such as tetrad, homologous chromosome, and zygote.
Schedule
1. Quiz #1 ­ Compare and Contrast Meiosis and Mitosis
2. Notes on stages of Meiosis
3. Start Pipe cleaner activity as a class.
Feb 10­2:10 PM
Meiosis Cell division which produces GAMETES containing HALF the number of chromosomes as the original cell.
In Humans
• Men = sperm • Women = egg
We have 46 chromosomes in our cells, therefore our gametes have 23
example
Feb 10­7:27 AM
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Day 3 ­ Notes and Activity.notebook
February 13, 2014
Zygote
forms when an egg joins with a sperm (fertilization)
Feb 10­7:39 AM
Haploid vs. Diploid
Diploid ­ cells that have 2 of each kind of chromosome (a pair).
Human diploid number per cell = 46
Most of your cells are like this.
Body cells: muscle, heart, skin, etc
Haploid ­ cells that have only HALF of the chromosomes. Human haploid number per cell = 23
These occur in our gametes.
(Result of Meiosis)
Feb 10­7:44 AM
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Day 3 ­ Notes and Activity.notebook
February 13, 2014
Homologous Chromosomes
• Matched set of chromosomes
• Matched based on the genes that are present and the size. • Humans have 23 pairs of homologous chromosomes.
Alleles can be different like "A" matches with "a"
But, the genes must be the same. J
A
M
M
Not a match
Feb 10­7:57 AM
Crossing Over
Occurs during Prophase 1 of Meiosis.
Alleles trade places between NON SISTER chromatids of
homologous pairs.
Source of genetic variation, along with independent assortment and segregation (Mendel's Laws)
Feb 10­8:17 AM
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Day 3 ­ Notes and Activity.notebook
February 13, 2014
One pair of Homologous Chromosomes before Interphase of Meiosis
Homologous Chromosomes after interphase of Meiosis
What has happened? • Prophase 1 of Meiosis
• Grouping is called a Tetrad
• Crossing Over is occurring
After Crossing Over.
What has happened to the alleles?
What would the gametes look like?
Feb 10­10:12 AM
We have 23 pairs of homologous chromosomes that this can happen in!
Feb 10­8:29 AM
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Day 3 ­ Notes and Activity.notebook
February 13, 2014
Feb 10­8:31 AM
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CHROMOSOME ABERRATIONS