1. MEIOSIS

2. Meiosis
Process in which the # of chromosomes per cell is cut in half by separating homologous chromosomes in a diploid cell.

3. Homologous
Chromosomes that each has a corresponding chromosome from the opposite-sex parent.

4. Diploid
A cell that has both sets of homologous chromosomes. Referred to as 2N. In a human = 46

5. Haploid
Gametes of sexually reproducing organisms. They have a single set of chromosomes and only a single set of chromosomes. Referred to as N. In a human = 23.

6. Gamete
Sex cell – sperm or egg

7. Meiosis – overall results
Start with 1 diploid cell and end with 4 haploid cells. All 4 sperm cells survive but only 1 out of the 4 eggs survive.

8. Phases
Meiosis I and meiosis II.

9. Meiosis I ( in humans)
Start with 46 chromosomes. They double to 92. They each separate into 2 cells with 46 chromosomes

10. Meiosis I - stages Interphase: chromosomes replicate
Prophase I: the replicated chromosome pairs up with its corresponding homologous chromosome. These pairs now form a tetrad.

11. Crossing over parts of the chromosomes exchange DNA result: new genetic combinations in the cell

12. CROSSING OVER (in Meiosis I)

13. Advantages to sexual reproduction
It promotes genetic variability. The offspring, because of crossing over, may have an advantage to handle the changing environment.

14. Metaphase I and Anaphase I

15. Telophase I and Cytokinesis
2 cells are now formed

16. Meiosis II Start with 2 cells with 46 chromosomes each.
They each divide producing 4 cell which each have 23 chromosomes

17. Prophase II

18. Metaphase II and Anaphase II

19. Telophase II

20. Cytokinesis II

21. Gamete formation- Gametogenesis
The end result of meiosis is either:
4 ovules (eggs) of which only 1 is used in reproduction
4 spermatids which are all used

22. Specifics - begins at puberty - sperm are stored in the epididymis
The formation of sperm = spermatogenesis
- begins at puberty
- sperm are stored in the epididymis
The formation of eggs = oogenesis
- begins prenatally (before the baby girl
is born).
- ovules are stored in the ovaries

23. Gametes to Zygotes
After the gametes are fertilized it is called a zygote. The zygote then undergoes mitosis to form an organism.

24. Mitosis vs. meiosis
Mitosis – results in 2 genetically identical diploid cells
Meiosis – results in 4 genetically different haploid cells

25. Gene Map
Shows exactly where each gene is located on a chromosome

26. Gene Linkage
When genes are located near each other on the same chromosome, they tend to stay together during crossing over. Therefore certain traits appear together in an organism at a higher frequency. Ex: blue eyes and blond hair

27. Watch AB, ab, CDE, cde

28. MEIOSIS SQUARE DANCE

29. NGSS
HS-LS3-1 HS-LS3-2 LS1.B