1. Meiosis
Making ME!

2. SEX CHROMOSOMES are Chromosomes that Determine the SEX of an Organism.
In Humans, Sex Chromosomes are either X or Y. 
Females have TWO X Chromosomes (XX) and
Males have an X and Y Chromosome.
TWO of the 46 Human Chromosomes are Sex Chromosomes
All the Other Chromosomes in an Organism are called AUTOSOMES (body cells).
44 of the 46 chromosomes are Autosomes.

3. The Chromosomes in the Zygote exist in PAIRS. 
For every Chromosome that was in the egg, there is a matching Chromosome from the sperm.
Human and Animal Chromosomes are categorized as either SEX CHROMOSOMES or AUTOSOMES.

4. Crossing Over

5. Figure 11-15 Meiosis Meiosis I Interphase I
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.

6. Figure 11-15 Meiosis Meiosis I Interphase I Prophase I
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Each chromosome pairs with its corresponding homologous (same genes at the same point) chromosome to form a tetrad.
Pairing up is called synapsis.
Crossing over may occur
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.

7. Figure 11-15 Meiosis Meiosis I Metaphase I
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
Move to the equator
The fibers pull the homologous chromosomes toward the opposite ends of the cell.

8. Figure 11-15 Meiosis Meiosis I Anaphase I
Section 11-4
Meiosis I
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.

9. Telophase I and Cytokinesis
Nuclear membranes form. The cell separates into two cells.
Haploid (2N) in Number.
Half the original number of chromosomes

10. Figure 11-17 Meiosis II Prophase II
Section 11-4
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

11. Figure 11-17 Meiosis II Metaphase II
Section 11-4
Meiosis II
Metaphase II
Prophase II
Anaphase II
Telophase II
The chromosomes line up at the equator in a similar way to the metaphase stage of mitosis.
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

12. Figure 11-17 Meiosis II Anaphase II
Section 11-4
Meiosis II
Anaphase II
Prophase II
Metaphase II
Telophase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

13. Figure 11-17 Meiosis II Telophase II
Section 11-4
Meiosis II
Telophase II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

14. Meiosis animation:

15. Comparison of Meiosis and Mitosis