Meiosis

1. Meiosis is the process in which the chromosomes in a parent cell are reduced to half. The process results in four gamete (sex) cells.

1.1. There are many steps in Meiosis: Interphase, Prophase 1, Metaphase 1, Anaphase 1, Telophase 1 and Cytokinesis, Prophase 2, Metaphase 2, Anaphase 2, and Telophase 2 and Cytokinesis.

1.2. Before we begin, we have to address Diploid vs. Haploid. The cells going into Meiosis are Diploid, meaning it contains two complete sets of chromosomes, one from each parent. After the meiotic cell cycle, it is Haploid, meaning it has half the number of chromosomes.

2. Prophase I

2.1. Homologous chromosomes pair up

2.2. Cross over occurs

2.2.1. Cross-over is when chromosomes cross over each other and exchange genes

3. Anaphase I

3.1. Chromosomes move away from pairing

3.2. Independent Assortment

4. Interphase

4.1. (2n)

4.2. Nucleus dissapears

4.3. Centrosomes move to opposite sides of cell

4.3.1. A centrosome is an organelle near the nucleus of a cell that contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division.

4.4. Chromosomes become visable

4.5. DNA is copied

5. Metaphase I

5.1. Chromosomes line up in the middle of the cell

5.2. Meiotic spindle fibers appear

5.3. Spindle fibers attach to centromeres

6. Telophase I & Cytokinesis

6.1. Cell pinches together

6.2. Cytoplasm splits between the two cells

6.3. Nucleus reappears

6.4. results in 2 daughter cells being present

7. Result of Meiosis I

7.1. 4 sets of chromatids

8. Prophase II

8.1. 2 daughter cells are present

8.2. Nucleus disappears

8.3. Spindle fibers form

9. Metaphase II

9.1. Chromosomes line up in the middle of the cell

9.2. Spindle fibers attach to centromeres

10. Anaphase II

10.1. Sister chromatids are pulled apart

11. Telophase II & Cytokinesis

11.1. Cells pinch together

11.2. cytoplasm separates

11.3. nucleus forms in all cells

11.4. results in 4 cells

12. *Results of Meiosis

12.1. 4 daughter cells

12.2. Haploid (n)