1. Meiosis

2. Meiosis
The process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
2 divisions, Meiosis 1 and Meiosis 2
Division of the sex cells (haploid cells)

3. Homologous Chromosomes
Chromosomes in which one set comes from Dad and one set comes from Mom
Similar in size, shape and banding pattern but not genetically identical

4. Diploid versus haploid cells
Diploid – having 2 sets of inherited chromosomes , 2 sets of genes
Ex. – all body or somatic cells
Represented by 2N
Haploid – having only 1 set of chromosomes, 1 set of genes
Ex. – sex cells
Represented by N

5. Meiosis
1 diploid cell (spermatocyte or oocyte) that contains 46 chromosomes
2 sets of divisions, 2 PMAT minus the interphase in the middle
Ends with 4 haploid cells

6. Meiosis I – cell has undergone interphase
Prophase 1
Homologous chromosomes come together, forms a tetrad (4 chromatids)
Crossing over – process where the chromatids of non-sister chromatids cross, break off, and exchange genetic material
Produces chromatids with new combination of alleles – GENETIC VARIATION – one reason we are not identical to each other.

7. Metaphase I and Anaphase I
Paired homologous chromosomes line up across the center of the cell
Anaphase I
Spindle fibers pull each homologous chromosome pair toward opposite ends of the cell

8. Telophase I and cytokinesis
Nuclear membrane forms around each cluster of chromosomes
Cytokinesis
Forms 2 new cells

9. Meiosis II – no interphase, no DNA replication
The final four phases of meiosis II are similar to those in mitosis. However, the result is four haploid daughter cells.
Prophase II
Chromosomes, consisting of two chromatids, become visible
NO homologous chromosomes

10. Metaphase II and Anaphase II
Chromosomes line up at the middle of the cell
Anaphase II
Paired chromatids separate

11. Telophase II and Cytokinesis -
4 Genetically different haploid cells

12. Comparing Mitosis and Meiosis
Similarities:

13. Comparing Mitosis and Meiosis
Differences: