1. Meiosis
How to make SEX cells!

2. What is Meiosis?
Most living things have body cells and sex cells (sperm and eggs)
Eggs are female sex cells
Sperm are male sex cells
Meiosis is a special cell division that results in sex cells

3. What’s the Big Picture?
In meiosis, a cell divides twice making a total of how many cells? 4

4. What’s the Big Picture?
1st time, each chromosome in a pair move away from its partner, each chromosome goes to a different cell, sister chromatids stay joined together
2nd division – sister chromatids separate

5. Some Terms:
Cells that have the normal number of chromosomes are called “Diploid”
Cells that have ½ the normal number of chromosomes are called “Haploid”
Meiosis results in 4 Haploid cells that are genetically different from each other (and remember the parent cell was diploid)

6. Some Terms:
Cells have pairs of chromosomes each chromosome in a pair is “homologous” to the other (they are homologs).
In meiosis the homologous chromosomes separate.

7. Interphase I
DNA Replicates

8. PROPHASE 1 Nuclear membrane begins to break down
Centrioles begin to move away from each other
Homologous (matching) chromosomes come together to form “tetrads” (remember: each chromosome has 2 strands of sister chromatids – now looks like 4 strands)

9. Metaphase 1 Sister chromatids become attached to fibers
Homologous chromosomes move to the center of the cell

10. Anaphase 1
Tetrads separate into double stranded chromosomes

11. Telophase 1 Cell membrane pinches cell into two
Nuclear membrane does not reform

12. Interphase II
DNA DOES NOT Replicate

13. Prophase II (2)
Centrioles double and form fibers again

14. Metaphase II (2)
Fibers connect chromatids and they line up at the middle

15. Anaphase II (2)
Fibers pull each strand apart to opposite ends of the cell

16. Telophase II (2) Cells Divide – Now have 4 cells
Each has ½ the # of Chromososmes (Haploid)
Each is genetically different from the others
Nuclear membrane reforms
Cell pinches off

17. The Whole Thing Part 1…

18. The Whole Thing Part 2…