1. Slide 1 of 35 Copyright Pearson Prentice Hall biology

2. Slide 2 of 35 Copyright Pearson Prentice Hall 11-4 Meiosis

3. Slide 3 of 35 Copyright Pearson Prentice Hall Each organism must inherit a single copy of every gene from each of its “parents.” Gametes are formed by a process that separates the two sets of genes so that each gamete ends up with just one set.

4. 11-4 Meiosis Slide 4 of 35 Copyright Pearson Prentice Hall Chromosome Number All organisms have different numbers of chromosomes.

5. 11-4 Meiosis Slide 5 of 35 Copyright Pearson Prentice Hall Chromosome Number These two sets of chromosomes are homologous (1) One chromosome is from the mother and the other chromosome is from the father

6. 11-4 Meiosis Slide 6 of 35 Copyright Pearson Prentice Hall Chromosome Number A cell that contains both sets of homologous chromosomes is said to be diploid (2) Symbol for diploid 2n=?

7. 11-4 Meiosis Slide 7 of 35 Copyright Pearson Prentice Hall Chromosome Number The gametes of sexually reproducing organisms contain a single set of chromosomes, and a single set of genes. These cells are haploid (3) – represented n.

8. 11-4 Meiosis Slide 8 of 35 Copyright Pearson Prentice Hall Phases of Meiosis Meiosis (4) - process of division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

9. Slide 9 of 35 11-4 Meiosis Copyright Pearson Prentice Hall Meiosis two divisions - meiosis I and meiosis II. By the end of meiosis II, the diploid cell that entered meiosis has become 4 haploid cells. Phases of Meiosis

10. Slide 10 of 35 11-4 Meiosis Copyright Pearson Prentice Hall Phases of Meiosis Meiosis I Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Interphase I Meiosis I

11. 11-4 Meiosis Slide 11 of 35 Copyright Pearson Prentice Hall Phases of Meiosis Each chromosome pairs with its corresponding homologous chromosome to form a tetrad (5) There are 4 chromatids in a tetrad. MEIOSIS I I Prophase I

12. Slide 12 of 35 11-4 Meiosis Copyright Pearson Prentice Hall Phases of Meiosis When homologous chromosomes form tetrads in meiosis I, they exchange portions of their chromatids in a process called crossing-over (6) Crossing-over produces new combinations of alleles.

13. Slide 13 of 35 11-4 Meiosis Copyright Pearson Prentice Hall Phases of Meiosis Meiosis II Telophase II and Cytokinesis Prophase II Metaphase II Anaphase II Telophase I and Cytokinesis I Meiosis II

14. 11-4 Meiosis Slide 14 of 35 Copyright Pearson Prentice Hall Phases of Meiosis Meiosis I – homologous chromosomes separate MEIOSIS II Prophase II

15. Slide 15 of 35 11-4 Meiosis Copyright Pearson Prentice Hall Phases of Meiosis Meiosis II – sister chromatids separate results in four haploid (N) daughter cells. MEIOSIS II Telophase II and Cytokinesis

16. 11-4 Meiosis Slide 16 of 35 Copyright Pearson Prentice Hall Gamete Formation In male animals, meiosis results in four equal-sized gametes called sperm.

17. 11-4 Meiosis Slide 17 of 35 Copyright Pearson Prentice Hall Gamete Formation In many female animals, only one egg results from meiosis. The other three cells, called polar bodies 7) are usually not involved in reproduction. The egg is called an ootid 8)

18. 11-4 Meiosis Slide 18 of 35 Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Mitosis results in the production of two genetically identical diploid cells. Meiosis produces four genetically different haploid cells.

19. 11-4 Meiosis Slide 19 of 35 Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Mitosis Same number of chromosomes and alleles as the original cell. allows an organism to grow and replace cells. Some organisms reproduce asexually by mitosis.

20. 11-4 Meiosis Slide 20 of 35 Copyright Pearson Prentice Hall Comparing Mitosis and Meiosis Meiosis half the number of chromosomes as the parent cell. genetically different from the diploid cell and from each other. sexually reproducing organisms produce gametes.

21. END OF SECTION