1. Starter Question 1. Take out a 1/2 of sheet of paper and answer the following question. You do NOT have to write the question. You MUST write in complete sentences. Q- Recall ch. 1 with the Characteristics of Life. How is cell division (mitosis) related to one or more of those characteristics?

2. Comparing Mitosis and Meiosis –Mitosis Cells produced by mitosis have the same number of chromosomes and alleles as the original cell. Mitosis allows an organism to grow and replace cells. Some organisms reproduce asexually by mitosis.

3. 11-4 Meiosis

4. Meiosis Similar in many ways to mitosis - M2Similar in many ways to mitosis - M2 Several differences howeverSeveral differences however –Involves 2 cell divisions –Results in 4 cells with 1/2 the normal genetic information. Vocabulary:Vocabulary: –Diploid (2N) - Normal amount of genetic material –Haploid (N) - 1/2 the genetic material. Meiosis results in the formation of haploid cells.Meiosis results in the formation of haploid cells. –In Humans, these are the Ova (egg) and sperm. –Ova are produced in the ovaries in females Process is called oogenesisProcess is called oogenesis –Sperm are produced in the testes of males. Process is called spermatogenesisProcess is called spermatogenesis Meiosis occurs in 2 phases: Meiosis 1 & Meiosis 2Meiosis occurs in 2 phases: Meiosis 1 & Meiosis 2

5. Chromosome Number- In book pg275 Chromosome Number –All organisms have different numbers of chromosomes. –A body cell in an adult fruit fly has 8 chromosomes: 4 from the fruit fly's male parent, and 4 from its female parent.

6. Chromosome Number These two sets of chromosomes are homologous. Each of the 4 chromosomes that came from the male parent has a corresponding chromosome from the female parent.

7. Purpose of Meiosis the number of chromosomes per cell is cut in half Homolgous chromosome in a diploid cell segregate (independently)

8. Meiosis involves two divisions, meiosis I and meiosis II. By the end of meiosis II, the diploid cell that entered meiosis has become 4 haploid cells. Video of Overview of Meiosis Phases of Meiosis

9. Meiosis I. Prior to division, amount of DNA doublesPrior to division, amount of DNA doubles

10. Phases of Meiosis Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. There are 4 chromatids in a tetrad. MEIOSIS I IProphase I

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

12. Metaphase 1 During metaphase 1 homologous chromosomes line-up along the metaphase plateDuring metaphase 1 homologous chromosomes line-up along the metaphase plate Areas of homologous chromosomes connect at areas called chiasmataAreas of homologous chromosomes connect at areas called chiasmata

13. Anaphase 1 During anaphase 1, each homologous chromosome is pulled to opposite sides of the cell. Unlike mitosis, THE CENTROMERES DO NOT BREAK.During anaphase 1, each homologous chromosome is pulled to opposite sides of the cell. Unlike mitosis, THE CENTROMERES DO NOT BREAK. Nuclei may or may not reform following division.Nuclei may or may not reform following division. Cytokenesis may or may not occur.Cytokenesis may or may not occur.

14. M1- Telophase & Cytokinisis

15. Phases of Meiosis so far Meiosis II Telophase II and Cytokinesis Prophase II Metaphase II Anaphase II Telophase I and Cytokinesis I Meiosis II

16. Same steps as MITOSISSame steps as MITOSIS DNA does not doubleDNA does not double Chromosomes randomly line-up along metaphase plate like regular mitosis.Chromosomes randomly line-up along metaphase plate like regular mitosis. During anaphase 2, CENTROMERES BREAK and each chromosome is pulled to opposite sides of the cell.During anaphase 2, CENTROMERES BREAK and each chromosome is pulled to opposite sides of the cell. Nuclei reform and cytokenesis usually occurs (although it is often unequal).Nuclei reform and cytokenesis usually occurs (although it is often unequal).

17. Overview of Meiosis Overview of Meiosis

18. Comparing Mitosis and Meiosis –Meiosis Cells produced by meiosis have half the number of chromosomes as the parent cell. These cells are genetically different from the diploid cell and from each other. Meiosis is how sexually reproducing organisms produce gametes.

19. Gamete Formation –In male animals, meiosis results in four equal- sized gametes called sperm.

20. Gamete Formation In female animals, only one egg results from meiosis. The other three cells, called polar bodies, are usually not involved in reproduction.

21. 11-4 –If the body cells of humans contain 46 chromosomes, a single sperm cell should have 46 chromosomes. 23 chromosomes. 92 chromosomes. between 23 and 46 chromosomes.

22. 11-4 –During meiosis, the number of chromosomes per cell is cut in half through the separation of daughter cells. homologous chromosomes. gametes. chromatids.

23. 11-4 –The formation of a tetrad occurs during anaphase I. metaphase II. prophase I. prophase II.

24. 11-4 –In many female animals, meiosis results in the production of only 1 egg. 1 egg and 3 polar bodies. 4 eggs. 1 egg and 2 polar bodies.

25. 11-4 –Compared to egg cells formed during meiosis, daughter cells formed during mitosis are genetically different, while eggs are genetically identical. genetically different, just as egg cells are. genetically identical, just as egg cells are. genetically identical, while egg cells are genetically different.