Chapter 11-4: Meiosis

1. Chapter 11-4: Meiosis Production of Sex Cells

2. Introduction • Mitosis and Meiosis are somewhat similar, but have 2 completely different goals. • Mitosis used in growth, healing, and reproduction in unicellular organisms. Whereas, Meiosis is SOLELY used for the production of gametes (sex) cells in multicellular organisms.

3. Mitosis VS. Meiosis M Process: 1 round of division. Start: 2n Process: 2 rounds of division Start: 2n End result: 4 genetically different daughter cells Finish: n End Result: 2 identical daughter cells Finish: 2n

4. Humans have two full sets of chromosomes • (one set from our male parent and one from our female parent.)

5. Each pair of chromosomes are known as “homologous” because they share the same genes, but likely very different alleles.

6. Ploidy: How many sets of chromosomes an organism has. • Because we (humans) have two complete sets of chromosomes, we are said to be diploid.

7. Ploidy Homologous pair The diploid number is referred to as 2N. For humans, 2N = 46. Each human somatic or body cell contains 46 chromosomes. Human Karyotype

8. Ploidy Each human gamete or sex cell only has a single set of chromosomes and are referred to as haploids. Human Karyotype

9. For our sperm or eggs, the haploid number is 23. • ________ = _______ (sperm and eggs) • ________ = _______ (every other cell in our body) n 23 2n 46 http://www.angelbabygifts.com/ Image by Riedell Image by Riedell n n 2n EGG +  SPERM haploid haploid diploid http://www.acmecompany.com/stock_thumbnails/13217.forty-six_chromosomes.jpg

10. The Process of Meiosis- click How are haploid (N) gamete cells produced from diploid (2N) cells? Meiosis is a process of reduction and division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.

11. Watch carefully! Diploid number? 4 chromosomes Homologous pairs? 2 pairs http://www.tokyo-med.ac.jp/genet/anm/mimov.gi

12. INTERPHASE By the end of G2, meiosis is ready to begin. MEIOSIS I

13. PROPHASE I MEIOSIS I

14. METAPHASE I MEIOSIS I

16. ANAPHASE I MEIOSIS I

17. TELOPHASE I MEIOSIS I

18. End of Meiosis I: If female – the process pauses here until the menstrual cycle begins during puberty. Once a month, one egg is released and may entire Meiosis II if fertilized. If male – the process does not pause, it goes right into Meiosis II. No time wasted to make sperm!!

19. PROPHASE II MEIOSIS II

20. METAPHASE II MEIOSIS II

21. ANAPHASE II MEIOSIS II

22. TELOPHASE II MEIOSIS II

23. 11.4 Meiosis Notice how meiosis differs between males and females. Spermatogenesis: Creates 4 genetically different sperm

24. Spermatogenesis – creation of sperm • Occurs in testes • Prompted by testosterone • Creates 4 cells

25. Notice how meiosis differs between males and females. Oogenesis: Creates 1 viable egg and 3 polar bodies that are digested by lysosomes.

26. Oogenesis • Occurs in ovaries • Born with a finite number of primary oocytes • Creates 1 egg and 3 polar bodies

27. Sperm structure

28. Timeline

29. 11.4 Meiosis Mitosis resulted in the production of two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells.

30. 11.4 Meiosis Summary of MITOSIS: (Genetically Identical) Mitosis allows an organism's body to grow and replace cells. In asexual reproduction, a new organism is produced by mitosis of the cell or cells of the parent organism.

31. 11.4 Meiosis Summary of MEIOSIS: (Genetically Different) A diploid cell but produces four haploid (N) cells. These cells are genetically different from the diploid cell and from one another. Meiosis is how sexually reproducing organisms produce gametes.

32. LET SLEEPING DOGS LIE

33. http://www.youtube.com/watch?v=6z3tafuoN0k National Geographic in the womb. Start at 5:30 http://www.angelbabygifts.com/ Image by Riedell Image by Riedell n _ __ EGG +  SPERM diploid haploid ________