1. Meiosis Gamete Production

2. MEIOSIS
Meiosis is specialized cell division resulting in sex cells with half the genetic material of the parents
Sex cells called GAMETES have exactly one set of chromosomes, this state is called haploid (1n)
Regular body (somatic) cells have 2 sets of chromosomes, this state is called diploid (2n) and divide through mitosis

3. (not in notes- write!)
Humans have a TOTAL of 46 chromosomes (DNA) in each body cells.
For a human baby, you need to pair up the chromosomes. Mom gives haploid cell (N=23) egg, Dad gives haploid cell (N=23) sperm
*If a cat’s egg has 10 chromosomes, how many would be found in the diploid cell?
*If a dog has 38 chromosomes in the heart cell, how many will be found in the sperm cell?

4. Meiosis
Produce 4 daughter cells with different amount and different type of DNA
These cells are Haploid (1n) gamete: sex cells
Ex. of gametes are sperm, egg, and pollen
Meiosis is for sexual reproduction
Sexual reproduction is 2 parents give DNA

5. Gametes Are Haploid
Gametes must have half the genetic material of a normal cell
If the genetic material in the gametes was not halved, when they combined the zygote would have more genetic material than the parents.
THAT WOULD BE A MUTATION!

6. *DNA does not replicate again
Stages Of Meiosis
Meiosis resembles mitosis except that it is actually two divisions not one
These divisions are called Meiosis I and Meiosis II
Meiosis I
Interphase (DNA Replicates)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis (2 daughter cells)
Meiosis II
*DNA does not replicate again
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II
(4 HAPLOID daughter cells)

7. Stages Of Meiosis: Meiosis I
Interphase
Mother cell
Prophase I:
Condensing Chromosomes
Prophase I:
Tetrad formation/
crossing over
Metaphase I
Anaphase I
Telophase I
Meiosis II

8. Stages Of Meiosis: Meiosis II
Telophase I
Prophase II
The products of meiosis are 4 haploid cells each with a unique set of chromosomes.
Metaphase II
*The products of mitosis are 2 diploid cells with identical chromosomes.
Anaphase II
Telophase II

9. Crossing Over
Crossing over- A process occurring during meiosis (Prophase I) where two chromosomes pair up and exchange segments of their genetic material.
This is how we get genetic variation which means that even though you and siblings have the same parents- you all look different! (except for identical twins)

10. Crossing Over Prophase I: Metaphase I Anaphase I Telophase I
Tetrad formation/
crossing over
Metaphase I
Anaphase I
Telophase I
Because of crossing over, every gamete receives a unique set of genetic information.
Telophase II

11. In The Beginning…
Two sex cells, a sperm and an egg, unite through the process of FERTILIZATION to form a zygote, the single cell from which the organism develops
Meiosis is the process of producing sperm and eggs (gametes)
*remember mitosis is to produce body (diploid) cells

12. Fertilization Results In A Diploid Zygote
Egg 1n
Haploid
nucleus
Sperm 1n
Haploid
nucleus

13. Fertilization Results In A Diploid Zygote
Egg 1n
Haploid
nucleus
Sperm 1n
Haploid
nucleus

14. Fertilization Results In A Diploid Zygote
Egg 1n
Haploid
nucleus
Haploid
nucleus
Sperm 1n

15. Fertilization Results In A Diploid Zygote
Egg 1n
Haploid
nucleus
Haploid
nucleus
Sperm 1n

16. From Zygote to Embryo
Zygote 2n
Zygote 2n

17. From Zygote to Embryo
MITOSIS now takes over to make a baby!

18. From Zygote to Embryo
Cleavage

19. From Zygote to Embryo
Cleavage

20. From Zygote to Embryo
Cleavage

21. From Zygote to Embryo

23. Compare Mitosis vs. Meiosis
Interphase (DNA replicates)
Prophase
Metaphase
Anaphases
Telophase
(Cytokinesis)
Final Product
2 identical cells
Same DNA
2 sets of chromosomes
Type of cell : Diploid (2N) Body cell
Meiosis
Interphase (DNA Replicates)
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis (2 daughter cells)
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II
Final Product
4 gamete different cells
Mixed DNA
1 set of Chromosomes
Type of cell: Haploid (N) gamete/sex cell

24. When does mitosis occur. What kinds of cells are produced
When does mitosis occur? What kinds of cells are produced? When does meiosis occur? What kinds of cells are produced?

25. Video
Amoeba sisters: Meiosis

26. The
End