1. Do Now What is the purpose of Mitosis?
If a cell that has 12 chromosomes in interphase goes through mitosis, how many chromosomes will be in each cell?
How is a baby made? (on a CELLULAR level…)

2. Objectives To list the steps of Meiosis.
To compare and contrast Meiosis and Mitosis.
To explain why Meiosis is necessary.

3. Meiosis Purpose: to make sex cells Gamete: sex cell Male gamete= sperm
Female gamete= egg (ovum)

4. Lets take a look at our cells
Our somatic cells contain 46 chromosomes
1 chromosome from Mom, and 1 from Dad. These are called homologous chromosomes.
Each gamete (sex cell) contains only 23 chromosomes!
Why are there are only 23 chromosomes in our sex cells?

5. Diploid vs. Haploid Diploid cell Haploid cell
Any cell with 2 homologous chromosomes
Abbreviated as 2n
Haploid cell
Any cell with a single chromosome set
Abbreviated as n

6. How do we become a Diploid Zygote?
Haploid egg cell fuses with haploid sperm cell in a process called Fertilization.
Half from mom and half from dad make up our homologous chromosomes! (23 pairs)
Our cells then undergo mitosis to create us.
But how did our parents create the sex cells to produce us?

8. How do we become a Diploid Zygote?

9. Meiosis Meiosis I and Meiosis II Each are similar to mitosis
Produces 4 daughter cells
Phases are still IPMAT, however there are two of each of the PMAT phases.

10. Prophase I
Pairing of homologous chromosomes occurs forming a tetrad. (synapsis)
Nuclear envelope breaks down.
Crossing over can occur- homologous chromosomes exchange genetic material.

11. Metaphase I Chromosome centromeres attach to spindle fibers
Homologous chromosomes line up at the equator.

12. Anaphase I
Homologous chromosomes separate and move to opposite poles

13. Telophase I The spindles break down.
Chromosomes uncoil and form two nuclei.
The cell divides.

14. Prophase II
A second set of phases begins as the spindle apparatus forms and the chromosomes condense.

15. Metaphase II A haploid number of chromosomes line up at the equator
Sister chromatids line up

16. Anaphase II
The sister chromatids are pulled apart at the centromere by spindle fibers
Move toward the opposite poles of the cell.

17. Telophase II
The chromosomes reach the poles, and the nuclear membrane and nuclei reform.

18. Cytokinesis Cytokinesis results in four haploid cells
Each with n number of chromosomes.