1. MEIOSIS AND SEXUAL REPRODUCTION
Cell Division
Of Sex Cells
MEIOSIS AND SEXUAL REPRODUCTION

2. What Are Sex Cells
Sex cells, or gamates, are different from body cells.
Body cells produce new tissues. Sex cells produce new organisms!

3. What Are Sex Cells The male sex cell is a SPERM
The female sex cell is an EGG

4. Sexual Reproduction
Sexual Reproduction – two sex cells, usually an egg and a sperm, come together.

5. Sexual Reproduction
Fertilization – the joining of an egg and a sperm, generally from two different organisms of the same species.

6. After Fertilization
When fertilization occurs, a zygote forms!

7. ? Question ?
Will the offspring resulting from sexual reproduction be identical to the parents?

8. How Do Sex cells divide?
Sex cells DO NOT divide by mitosis. They divide though another process called meiosis.

9. Sex cells have HALF the number of chromosomes compared to body cells!
Mitosis
Meiosis
Happens in BODY CELLS.
These are called diploid cells because they contain 23 pairs of chromosomes
(46 single chromosomes)
Happens in SEX CELLS.
These are called haploid cells because they contain 23 single chromosomes
Sex cells have HALF the number of chromosomes compared to body cells!

10. What is Diploid What is Haploid
Diploid cells (2N) have two complete sets of chromosomes.   The body cells of animals are diploid.
Haploid cells have one complete set of chromosomes.  In animals, gametes (sperm and eggs) are haploid.

11. What is Meiosis
Meiosis uses two cell divisions.
Meiosis
In A
Nutshell

12. Meiosis
Meiosis deals only with sex cells. Each sex cell (sperm or egg) has a chromosome from each parent. Before division, these cells duplicate.
Arthur’s sex cell

13. Meiosis I
In Meiosis I, the nucleus divides and produces two new cells. Each new cell has one duplicated chromosome from each similar pair.

14. Meiosis I

15. Meiosis I

16. Meiosis I

17. Meiosis I

18. Meiosis I

19. Meiosis I

20. Meiosis I

21. Meiosis I

22. Meiosis I

23. Meiosis I

24. Meiosis II
In Meiosis II, the nuclei divide and the chromatids separate, producing four cells with half the number of chromosomes of the original nucleus.

25. Meiosis II

26. Meiosis II

27. Meiosis II

28. Meiosis II

29. Meiosis II

30. Meiosis II

31. Meiosis II

32. Meiosis II

33. Meiosis II

34. Meiosis Il

35. Meiosis Il

36. Meiosis Il Thanks to Meiosis, Arthur now has 4 sex cells! Yay!
Will these sex cells become sperm or eggs?
Thanks to Meiosis, Arthur now has 4 sex cells! Yay!

37. To Simplify
Meiosis
In A
Nutshell

39. 2n
Meiosis I n n
Meiosis II n n n n