1. Unit 5: Cell Growth and Development 5.5 Meiosis

2. Process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Diploid cell becomes 4 haploid cells (gametes)
Without meiosis, the number of chromosomes would double in each generation
Meiosis

3. Meiosis I
Prophase I
Metaphase I
Anaphase I
Telophase I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

4. Prophase I: Each pair of homologous chromosomes pair up
Chromosomes form a tetrad: 4 chromatids
Crossing over: Homologous chromosomes exchange sections of DNA, producing new combinations of alleles.
Stage 1 of Meiosis I

6. Metaphase I: Paired homologous chromosomes line up on the equator of the cell
Stage 2 of Meiosis I

7. Anaphase I: Spindle fibers pull chromosomes toward opposite ends of the cell.
Each chromosomes still has 2 chromatids
Stage 3 of Meiosis I

8. Telophase and Cytokinesis: Nuclear membrane forms around each cluster of chromosomes. Cytokinesis follows..
Results in two daughter cells
Neither has a complete set of chromosomes
Stage 4 of Meiosis I

10. Prophase II: Chromosomes, consisting of two chromatids, become visible
No tetrads, because they already separated.
Stage 1 of Meiosis II

11. Stage 2-4 of Meiosis II
Metaphase II  Cytokinesis: Similar to meiosis I
Result is four haploid daughter cells

15. When two haploid cells combine, they form a zygote: the first cell of a unique individual