Cell Division (chapter 12 and 13)

1. Cell Division(chapter 12 and 13) AP Biology Miss Hanna

2. Cell Division • Process by which cell produces more of their kind • Prokaryotes- binary fission • Eukaryotes- mitosis and meiosis

3. Prokaryote • Simple single-celled organism without nucleus • Genetic material • single circular chromosome of DNA, anchored to cell membrane • Duplicated before division

4. Cell Division in Prokaryotes Elongate until double in size Binary Fission- Cell pinches in and separates into 2 identical daughter cells

5. Cell Cycle • Functions as the daily planner of growth and development • 4 main stages- • G1 phase- growth phase • S phase- DNA is duplicated • G2 phase- growth phase • M phase- mitosis- cell division

6. Stages of Cell Cycle • G1 phase- • cell prepares itself for the synthesis stage of the cycle • making sure it has all the necessary raw materials for DNA synthesis • S phase- • DNA is copied so that each daughter cell has a complete set of chromosomes

7. Stages of Cell Cycle • G2 phase- • prepares itself for mitosis and/or meiosis • Making sure all it has raw materials needed for separation and formation of daughter cells • M phase- • Mitosis • Cell separates into two new cells

8. Interphase • First 3 stages of the cycle (G1, S, G2) • Chromosomes invisible • organelles double • 90% of time spent in this phase • 10% spent in mitosis • Time needed to complete cycle varies • Skin cells continually replicate • Nerve cells do not replicate

9. Interphase

10. Mitosis • Purpose of eukaryotic asexual reproduction, growth and repair • 4 stages • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis- physical separation of newly formed daughter cells

11. Chromatin Raw material that gives rise to chromosomes Long and thin during interphases Condenses and becomes visible under microscope in mitosis

12. Prophase Nucleus and Nucleolus disappear Chromosomes appear as connected sister chromatids Mitotic spindle (made of microtubles) begins to form Centrosomes (pair centrioles) move to opposite ends of cell (plant cells do not have centrioles)

13. Prophase

14. Metaphase(Middle) Sister chromatids line up along the middle of the cell Ready to split

15. Anaphase(Apart) Sister chromatids split move on microtubles to opposite poles in cell Spindle apparatus pulls sister chromatids to opposite poles

16. Telophase Nuclei of newly split cells form Nucleoli appear Chromatin uncoils

17. Cytokinesis (Magic!) Newly formed daughter cell splits apart Animal cells split by a cleavage furrow Plant cells split by formation of cell plate

18. Important Vocabulary Cell plate- plant cell structure, made in golgi apparatus, composed of vesicles that fuse together along the middle of the cell, completing the separation process

19. Important Vocabulary Cleavage Furrow- formed (in animal cells) between the two daughter cells that pinch together to complete separation after mitosis

20. Important Vocabulary Cytokinesis- actual splitting of the newly formed daughter cell Mitosis spindle- made of microtubles that assists the cell in physical separation of chromosomes during mitosis

21. Mitosis

22. Control of Cell Division • Important to normal cell growth • Ways cells control process of cell division • Checkpoints • Density-dependent inhibition • Growth factors • Cyclins and protein kinases

23. Control of Cell Growth • Checkpoints- • During cell cycle verifies enough nutrients and raw materials needed for next stage of the cycle • Density-dependent inhibition- • certain density of cell reached, growth slows or stop b/c not enough raw materials • Cells halted and enter a quiescent phase of cell cycle G0 • Cancer cells lose inhibition and grow out of control

24. Control of Cell Growth • Growth factors- • Assist in the growth of structures of cell • Cyclins and protein kinases • Cyclins- protein that accumulates during G1, S and G2 phase • Protein kinases- protein that controls other proteins through addition of phosphate groups

25. Cyclins and Protein Kinase Cyclin dependent kinase (CDK) present throughout cell cycle Binds with cyclin to form MPF (mitosis promoting factor) Early in cell cycle, cyclin and MPF low As concentrations of cyclin and MPF reach threshold—pushes cell into mitosis As mitosis proceeds, cyclin and MPF decreases pulling cell out of mitosis

26. Haploid vs. Diploid • Haploid (n)- organism with only 1 copy of each chromosome • Sex cells • Human gametes (sex cells)- 23 chromosomes • Diploid (2n)- organism with 2 copies of each type of chromosome • Body cells • Human cells- 46 chromosomes

27. Meiosis • Occurs during sexual reproduction • Goes through cell cycle making copy of DNA but enters Meiosis instead of mitosis • Makes haploid cells (sex cells) • Two parts • Meiosis I • (prophase, metaphase, anaphase, telophase) • Meiosis II • (prophase II, metaphase II, anaphase II, telophase II)

28. Homologous Chromosomes Resemble one another in shape, size, function and genetic information Human 46 chromosomes divided into 23 homologous pairs One pair from mother, one pair from father Gametes- cells produced during meiosis

29. Meiosis I • Prophase I- • Chromosomes pair up • Crossover of genetic information (synapsis) • Nuclear envelope breaks, spindle fibers form • Metaphase I- • Chromosomes align on metaphase plate with homolog partner • Anaphase I- • Homologous pairs move to opposite poles of cell

30. Meiosis I Continued • Telophase I- • Nuclear membrane reforms; process of division begins • Cytokinesis- • Daughter cells split • Two newly formed cells are haploid (n)

31. Meiosis I

32. Meiosis II • Prophase II- • Nuclear envelope breaks apart, spindle fibers begin to form • Metaphase II- • Sister chromatids line up along equator of cell • Anaphase II- • Sister chromatids split, pulled toward poles • Telophase II • Nuclei and nucleoli reform • Cytokinesis • Newly formed daughter cells divide

33. Meiosis II

34. Meiosis I and II

35. Mitosis and Meiosis

36. Gamete Formation Spermatogenesis- leads to production of 4 haploid sperm during each meiosis cycle Oogenesis- leads to production of 1 ovum (egg) per meiosis cycle

37. Oogenesis • Meiosis I • One cell receices ½ genetic information • Polar body- other cell that receives ½ of genetic information is cast away • Meiosis II • Remaining cell divides again forming ovum and a polar body which is simply cast away

38. Fertilization Sperm (n) haploid cells meets up with egg (n) haploid cell to produce a diploid cell (2n) --zygote

39. Mitosis vs. Meiosis

40. Crossing Over Homologous pairs join together Occurs during Meiosis I –Prophase Pairs wrap around each other and exchange genetic information

41. Life Cycle • Cycle of events that make up reproductive cycle • 3 types of cycles • Plant life- alternation of generations • Human life cycle • Fungus life cycle

42. Plant life cycle Sporophyte- diploid cell(undergoes meiosis to produce haploid spore) Gametophyte- haploid cell—can do mitosis to produce more haploid cells

43. Human Life Cycle 2 haploid cells (n) (sex cells) come together Fertilization occurs produce zygote (2n) Zygote multiplies by mitosis Create multi-cellular organism (2n) Meiosis produce gametes (haploid sex cells –n)

44. Fungus Life Cycle 2 haploid cells (gametes) come together---fertilization Produce zygote (2n) multiplies by meiosis producing haploid organism(n) Gametes (sex cells) formed by mitosis Only diploid cell is the zygote

45. Sources of Genetic Variation Cell division Random determination of which sperm will meet which egg Crossing over