1. Gamete (sperm and egg) Production
Meiosis
Gamete (sperm and egg) Production

2. Meiosis Involves 2 cell divisions
Results in 4 cells with 1/2 the normal genetic information.
Start with 1 diploid end with 4 haploid
Vocabulary:
Diploid (2N) - Normal amount of genetic material
Haploid (N) - 1/2 the genetic material.

3. Meiosis In Humans, these are the Egg and sperm.
Meiosis results in the formation of haploid cells.
In Humans, these are the Egg and sperm.
Meiosis occurs in 2 phases: Meiosis I & Meiosis II

4. Meiosis I
Prior to division (S phase), amount of DNA doubles

5. Metaphase I
Metaphase I homologous chromosomes line-up along the metaphase plate or EQUATOR
Mom and dad chromosomes = homologous chromosomes

6. Crossing Over
Segments of homologous chromosomes break and reattach at similar locations.
Results in new genetic combinations of offspring.
This is the main advantage of sexual reproduction

7. Anaphase I
During Anaphase I, each HOMOLOGOUS CHROMOSOME is pulled to opposite sides of the cell.

8. Meiosis II
Chromosomes randomly line-up along metaphase plate like regular mitosis.
Start with 2 haploid and end with 4 haploid
Same steps as mitosis
Sister chromatids

9. Overview of Meiosis

10. Non disjunction
When sister chromatids or homologous chromosomes fail to separate

11. Trisomy 21 (Down Syndrome)
Non disjunction on the 21st chromosome)