1. Mrs. Stewart Biology I standard
MITOSIS VS. MEIOSIS
Mrs. Stewart
Biology I standard

2. REVIEW: Cell Cycle Mitosis Interphase M-phase (mitosis)
G1, S, and G2
M-phase (mitosis)
P-M-A-T-C
Mitosis
Asexual reproduction
Produces 2 identical daughter cells
Daughter cells are diploid
Daughter cells are identical to parent/mother cell

4. What differences can you see?
How many sets of chromosomes are in the cells that Meiosis produces?
How many cells does Meiosis produce?
How many divisions occur in Meiosis?

5. MEIOSIS:
The process of creating a gamete

6. Chromosomes come in matching sets -these are called homologous pairs

7. Karyotype after DNA replication
Notice how each chromosome has duplicated itself.

8. Final Products: Mitosis Meiosis
Somatic cells in your body have two sets of chromosomes - they are called DIPLOID  
Gametes (Sex cells-sperm and eggs) only have one set (half) of chromosomes  - they are called HAPLOID

9. What are the steps? Phases of Meiosis I Interkinesis
Prophase I
Metaphase I
Anaphase I
Telophase I
Cytokinesis
Interkinesis
Phases of Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II

11. Interphase Makes the diploid (2n) cell now be (4n)
DNA replicates
Makes the diploid (2n) cell now be (4n)
n=number of chromosome sets/pairs
Example: humans have 46 total chromosomes, so our diploid number is 2n or 2(23) where n = 23

12. Prophase I
Homologous chromosomes pair up (forming a tetrad) - Mom & Dad go on a date
Crossing over occurs
Chromatids MAY exchange portions of DNA
Leads to genetic variances

13. Telophase I and Cytokinesis
Metaphase I
Spindle fibers attach to the chromosomes
Homologous chromosomes line up in the middle of the cell
Anaphase I
Fibers pull the homologous chromosomes toward
opposite ends of the cell
Telophase I and Cytokinesis
Nuclear membranes form
Cell separates into two new cells

15. Meiosis II
The daughter cells from Meiosis I divide again WITHOUT replicating their chromosomes
That leads to 4 gametes, each with half the number of chromosomes (haploid) as the original “mother” cell

16. Telophase II and Cytokinesis
Metaphase II
Spindle fibers attach to the chromosomes
chromosomes line up in the middle of the cell – similar to how they do in Mitosis
Anaphase II
Fibers pull the sister chromatids toward
opposite ends of the cell
Telophase II and Cytokinesis
Nuclear membranes form
Both cells separate – forming 4 new haploid cells

18. Oogenesis – meiosis in human female reproductive cells – makes eggs (ovum)
Forms one egg cell with a large supply of stored nutrients.
The other 3 gametes produced, called polar bodies, disintegrate.

19. Produces 4 viable gametes
Spermatogenesis – meiosis in human male reproductive cells to make sperm (spermatazoa)
Produces 4 viable gametes
All 4 gametes produce a long whip-like tail

20. Meiosis: Cell division necessary for sexual reproduction
Produces 4 daughter cells
Daughter cells are Haploid
Daughter cells are gametes (sexual repro. cells)
2 nuclear/cellular divisions
Vital to maintain correct number of offspring in sexually reproducing organisms
Crossing over = opportunity for genetic variability

21. Differentiate Mitosis Meiosis Used for sexual reproduction
Produces 4 daughter cells
Daughter cells are Haploid
Daughter cells are genetically different from each other, and from parent cell
Produces gametes
Two nuclear/cellular divisions
Asexual reproduction
Produces 2 daughter cells
Daughter cells are diploid
Daughter cells are identical to each other and to parent cell
Produces somatic cells
One cell/nuclear division

22. Human chromosomal diseases
Down’s syndrome (extra chromosome #21)
Turner’s syndrome (missing or incomplete X chromosome in girls)
Klinefelter’s syndrome (males that have an extra X chromosome [XXY])
**Mistake in meiosis can lead to an incorrect chromosomal number, causing consequences for offspring**

23. Video
Meiosis square dance