1. MEIOSIS EQ: How is meiosis different from mitosis?

2. Chromosome DNA Gene

3. DIPLOID CELL = a cell with 2 of each kind of chromosome _______________ Chromosomes Mom 1 Dad 1 “Homologous” ?

4. “Complete Set” __  Mom __  Dad Dad 1 Mom 1 “__n” “autosomes” “sex chromosomes” 2 23 __Total 46

5. Most of the CELLS in YOUR body Dad 1 Mom 1 Dad 1 Mom 1

6. Haploid Cell = a cell with 1 of each kind of chromosome

7. “n” _____Total Chromosomes 23 or

8. “Gamete” (male/female) Haploid + Haploid = ? nn 2n “Zygote” ___ ________ 23 The first cell is called a

9. Chromosome Numbers Human: –Diploid 2n (somatic cell) = 46 –Haploid n (gamete) = 23 Fruit Fly 8/4 Garden Pea 14/7 Tomato24/12 Apple34/17 Chimp48/24 Adder’s tongue fern1260/630

10. WHY NOT ONLY MITOSIS? Mitosis produces an exact replica Each parent would give a complete set of chromosomes (46) Baby wouldn’t be Human

11. MEIOSIS = Sexual Cell Division Halving the chromosome #

12. 1 Body Cell  ? Replicate DNA once and Divide? Twice 4 Eggs or 4 Sperm

13. 1 Diploid (2n)  4 Haploid (n) 46 pairs 46 23 46

14. PHASES OF MEIOSIS Meiosis I Interphase PMAT I Meiosis II PMAT II

15. First Interphase Meiosis I 46 46 pairs 46

16. Meiosis II = 4 Gametes 46 23

17. 1 Diploid (2n)  ? 46 92 46 23 Interphase PMAT I PMAT II ? ? 4 Haploid (n)

19. Meiosis I occurs in four phases: prophase, metaphase, anaphase, and telophase. Interphase? Chromosomes replicate  Sister Chromatids Centrosomes

20. Prophase I = – the chromosomes condense and homologous chromosomes pair up to form tetrads. –At several sites the chromatids are crossed (chiasmata) and segments of the chromosomes are traded (“crossing over”).

21. Metaphase I = the tetrads are all arranged at the metaphase plate. Anaphase I = the homologous chromosomes separate and are pulled toward opposite poles.

22. Telophase I = –movement of homologous chromosomes continues until there is a set at each pole. –Each chromosome consists of linked sister chromatids. Cytokinesis = usually occurs simultaneously. “NO further replication of chromosomes”

23. Meiosis II is very similar to mitosis. Prophase II =

24. Metaphase II = Anaphase II =

25. Telophase II = Cytokinesis = End  ? four haploid daughter cells.

26. #?46 #? 46 23 each 92#?

27. Animation

28. P IM I A I T I ---------------- 4n 2n Interphase: Chromosome Duplicate

29. P II M II A II T II - - - - - - - - - - - - - - - - - -------------- ---------------- -------------- -------------- n n nn Interphase: No Duplication

30. Sperm (n) to Egg (n) = Zygote (2n)

31. Fertilization restores the diploid condition by combining two haploid sets of chromosomes.

33. GENETIC VARIABILITY Meiosis “shuffles” genetic information 3 ways of “shuffling”

34.  Dad  Mom “Independent Assortment” -------- --------

35. Human Gamete = 23n –Egg: 2 23 = 8.4 million –Sperm: 2 23 = 8.4 million Egg + Sperm = 70 trillion possibilities

36. “Recombinant Chromosomes” “Crossing Over”

37. “Random Fertilization” 200 – 500 million per ejaculation1 egg One “winner”

38. GENETIC VARIABILITY Evolutionary adaptation?

40. THE CELL CYCLE, MITOSIS, and MEIOSIS The Cell Cycle 2 Main Phases Time Spent in each What happens in all phases Stages of Interphase Chromosomes DNA Replication Mitosis Phases of Mitosis Cytokinesis Chromosomes vs. Chromatids Chromosome Number Diploid Somatic Cancer Meiosis Haploid Gametes Phases of Meiosis Tetrads Crossing Over Genetic Variability