1. WARM Up
Write everything you know/remember about mitosis

2. Meiosis Gamete Production
Texas Expected Knowledge and Skills (TEKS)
6G Recognize the significance of meiosis to sexual reproduction

3. Somatic Cells (Body Cells)
MEIOSIS
Meiosis is specialized cell division resulting in sex cells with half the genetic material of a body (somatic) cell. The process of making sperm and eggs (gametes).
Somatic Cells (Body Cells)
Gametes (Sex Cells)
Full set of chromosomes – Diploid (2n)
Divide via Mitosis (cell cycle)
Half a set of chromosomes – Haploid (1n)
Divide via Meiosis

4. Humans have a TOTAL of 46 chromosomes (condensed DNA) in each body cell.
For a human baby, mom gives a haploid egg (n=23) and dad gives a haploid sperm (n=23) to make a full set of 46 chromosomes.

5. Questions
*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?

6. Meiosis
Produces 4 daughter cells with diverse genetic chromosomes (DNA).
These daughter cells are Haploid (1n) gametes: sex cells
Examples: sperm, eggs, pollen
Meiosis is for: sexual reproduction
Sexual reproduction includes 2 parents contributing DNA.

7. Gametes must have half the genetic material of a body cell
If the genetic material in the gametes were not halved when they combined, the resulting offspring would have more genetic material than the parents.
This would be a MUTATION!
Mule
Zedonk

8. Process of Meiosis
During Meiosis, a cell divides twice, but only replicates its DNA once. This leads to four daughter cells with half the amount of genetic information.

9. Crossing Over
During meiosis chromosomes pair up and exchange segments of their genetic material in a process called crossing over.

10. Crossing Over Crossing over leads to genetic variation.
Crossing over is why siblings can have the same parents but still may look very different (except for identical twins etc.).

11. Question
What is the significance of crossing over to a population? Explain your answer

12. In The Beginning…
Fertilization: the process of two sex cells, a sperm and an egg, uniting.
Zygote: a single cell formed from the union of a sperm and egg which leads to a unique individual.

13. Fertilization Results In A diploid cell, a zygote
Egg n
Haploid
nucleus
Sperm n
Haploid
nucleus

14. Fertilization Results In A diploid cell, a zygote
Egg n
Haploid
nucleus
Sperm n
Haploid
nucleus

15. Fertilization Results In A diploid cell, a zygote
Egg n
Haploid
nucleus
Sperm n
Haploid
nucleus

16. Fertilization Results In A diploid cell, a zygote
Egg n
Haploid
nucleus
Sperm n
Haploid
nucleus

17. From Zygote to Embryo
Zygote 2n
Zygote 2n

18. From Zygote to Embryo
Once fertilization occurs, mitosis takes over allowing the cell to divide and grow into a unique individual.

19. From Zygote to Embryo
Cleavage

20. From Zygote to Embryo
Cleavage

21. From Zygote to Embryo
Cleavage

22. From Zygote to Embryo

24. Identical Twins Formed from one egg and one sperm.
Before the cells differentiate into specific types of cells, a clump of cells splits off from the whole group.
Both clumps will then differentiate into separate individuals with the same genetic makeup.

25. Identical Twins

26. Fraternal Twins Formed from two eggs and two sperm.
Non-identical siblings who are born at the same time.

27. Compare Mitosis vs. Meiosis
Final Product
2 identical cells
Same DNA
Full set of chromosomes
Type of cell : Diploid
(2N) Body cell
Meiosis
Final Product
4 gamete different cells
Mixed DNA
Half set of Chromosomes
Type of cell: Haploid (N) gamete/sex cell

28. Answer the following questions: When does mitosis occur
Answer the following questions: When does mitosis occur? ______ What kinds of cells are produced? ___ When does meiosis occur? ___ What kinds of cells are produced? ___

29. Video
Amoeba sisters: Meiosis

30. The
End