Chapter 10 Section 2 Notes- Meiosis

1. Chapter 10 Section 2 Notes-Meiosis

2. Section 10.2 Summary – pages 263-273 • Gene--A segment of DNA that controls production of a protein, exists on a chromosome • A chromosome--can contain a thousand or more genes along its length Chromosome

3. Section 10.2 Summary – pages ‘263-273 • In most animals and plants--chromosomes occur in pairs • Humans--have 23 pairs or 46 total chromosomes • Homologous chromosomes--The 2 chromosomes of a pair

4. Section 10.2 Summary – pages 263-273 • Diploid--A cell in which the chromosomes occur in pairs (2n) • Human body cells--are diploid and have a pair of each chromosome

5. Section 10.2 Summary – pages 263-273 • Haploid--A cell that contains only one chromosome from each pair (n) • Gametes--haploid sex cells. • male=sperm female=egg

6. Section 10.2 Summary – pages 263-273 Diploid and haploid cells Chromosome Numbers of Common Organisms • This table shows the diploid and haploid number of chromosomes of some species. Organism Body Cell (2n) Gamete (n) 4 Fruit fly 8 Garden pea 14 7 10 Corn 20 12 Tomato 24 Leopard Frog 26 13 Apple 34 17 Human 46 23 Chimpanzee 24 48 Dog 78 39 1260 630 Adder’s tongue fern

7. Section 10.2 Summary – pages 263-273ection 10.2 Summary – pages 263-273 • Fertilization--fusion of male and female gametes to form zygote • Zygote--diploid cell (2 of each chromosome) • Sexual reproduction--production and combination of gametes

8. Section 10.2 Summary – pages 263-273 • Meiosis--Cell division that produces gametes that have 1/2 the number of chromosomes as the parent cell (haploid) • Meiosis has--2 separate cell divisions, meiosis I and meiosis II Haploid gametes (n=23) Sperm Cell Meiosis Egg Cell Fertilization Multicellular diploid adults (2n=46) Diploid zygote (2n=46) Mitosis and Development

9. Section 10.2 Summary – pages 263-273Section 10.2 Summary – pages 263-273 • Meiosis begins with 1 diploid cell and ends with 4 haploid cells or gametes • Each gamete has half the number of chromosomes as a diploid cell Meiosis II 4 haploid cells with 2 chromosomes each 1 diploid cell with 4 chromosomes

10. Section 10.2 Summary – pages 263-273 Meiosis I • Prophase I • DNA coils into tetrads • Spindle forms • Crossing over--DNA is swapped between chromosomes in a pair

11. Section 10.2 Summary – pages 263-273 Meiosis I • Metaphase I • Tetrads (2 pairs of homologous chromosomes) line up along the equator of the cell

12. Section 10.2 Summary – pages 263-273 Meiosis I • Anaphase I • Tetrads are separated into chromosome pairs and move to opposite ends of the cell

13. Section 10.2 Summary – pages 263-273Section 10.2 Summary – pages 263-273 Meiosis I • Telophase I • Spindle disappears • Chromosomes uncoil • Cytoplasm divides into 2 cells

14. Meiosis II Section 10.2 Summary – pages 263-273 • Meiosis II--has 4 stages, prophase II, metaphase II, anaphase II, and telophase II • Each stage--occurs just like the stages of mitosis Prophase II Metaphase II Anaphase II Telophase II

15. Meiosis II • Prophase II: • A spindle forms in each of the 2 new cells • Spindle fibers attach to the chromosomes • Nuclear envelope disappear • Metaphase II • The sister chromatids line up in the middle of the cell at the equator.

16. Meiosis II • Anaphase II: • Centromere of the chromosomes split, allowing the sister chromatids to separate • The chromatids begin to move to the opposite ends of the cell

17. Meiosis II • Telophase II: • Sister chromatids reach opposite ends of the cell • Spindles disappear and the nuclear envelope appears • Cytoplasm divides

18. MEIOSIS

19. Comparison of Mitosis and Meiosis

20. Sect ion 10.2 Summary – pages 263-273Section 10.2 Summary – pages 263-/273 The Phases of Meiosis Click image to view movie.