MITOSIS VS. MEIOSIS

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

2. REVIEW: • Cell Cycle • Interphase • 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. Somatic cells in your body have two sets of chromosomes - they are called DIPLOID Final Products: Mitosis Meiosis 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 • Prophase I • Metaphase I • Anaphase I • Telophase I • Cytokinesis • Interkinesis • Phases of Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II • Cytokinesis

11. Interphase • 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. 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. 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. 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) • 2nuclear/cellulardivisions • Vital to maintain correct number of offspring in sexually reproducing organisms • Crossing over = opportunity for genetic variability

21. Differentiate Mitosis Meiosis • 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 • 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 • Twonuclear/cellular divisions

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