1. Meiosis

2. Meiosis is a form of cell division where diploid body cells make haploid gametes. In humans, this means cells that have 46 chromosomes (2N) divide into cells that have 23 chromosomes (N).

3. Check point 1. What is haploid? Half the number of chromosomes 2. How many chromosomes do diploid cells have? 46

4. Meiosis comes from a Greek word meaning “to make smaller”. This is because the number of chromosomes is reduced in meiosis. Example: Chromosomes are reduced from 2 to 1.

5. Meiosis makes haploid gametes. These are eggs in females, and sperm in males. When eggs are produced, it is called oogenesis. When sperm are produced, it is called spermatogenesis.

6. Check point 1. What process makes haploid gametes? Meiosis 2. Why do we need meiosis? To create sex cells with half the DNA from each parent

7. Meiosis happens in two stages called Meiosis I and Meiosis II.

8. Meiosis I

9. Check Point 1. What is the end result of Meiosis I? Two daughter cells 2. How many chromosomes does each daughter cell have after Meiosis I? 46

10. Interphase The cell grows and the DNA replicates (copies) the same way as in mitosis.

11. Pictures of chromosomes

13. Check Point 1. What does the centromere do? It holds the chromosomes together.

14. Prophase I: DNA condenses to form chromosomes. Homologous pairs of chromosomes come together.

15. Metaphase I : Homologous pairs line up on the equator of the cell.

16. Anaphase I : One member of each homologous pair of chromosomes moves to opposite ends of the cell.

17. Telophase I : Chromosomes gather to form two nuclei. The parent cell divides into two daughter cells. Each daughter cell has only one member of each homologous pair of chromosomes.

18. Interphase II During interphase II there is no DNA replication. This is also called interkinesis.

19. Check Point What is the difference between Interphase I and Interphase II? There is no DNA replication in interphase II.

20. Meiosis II

21. Check point 1. Prophase I and Prophase II different? –Prophase I starts with one cell Prophase II starts with two

22. Prophase II : Chromosomes condense again.

23. Metaphase II : Chromosomes line up on the equator of the cell.

24. Anaphase II : The chromosome copies, called chromatids, are pulled to opposite poles of the dividing cell. Anaphase II in corn Anaphase II in lily

25. Telophase II: The chromatids gather into four new nuclei. Four haploid daughter cells are produced.

26. Check Point What is the end result of Meiosis II? –Four haploid daughter cells

28. Meiosis comes from a Greek word meaning “to make smaller”. This is because the number of chromosomes is reduced in meiosis. Example: Chromosomes are reduced from 2 to 1.

29. Grasshopper Meiosis

31. Meiosis Activity