1. CELL DIVISION

2. Cell Division  One cell  Two identical cells  Cells must be able to pass on ALL information from their DNA  So DNA must be replicated before cell division occurs

3. Prokaryotic Cells  No nucleus  DNA is found as circular molecule  BINARY FISSION DNA replicates DNA replicates DNA attaches to membrane DNA attaches to membrane Cell pinches & splits Cell pinches & splits

4. Eukaryotic Cells  Much more complicated  Chromosome – DNA coiled around proteins

5. Formation of chromosomes  DNA at “rest” found unorganized in nucleus  Just before cell division, it organizes itself into chromosomes

6. Human Chromosomes

7. Parts of a Chromosome

8. UNDERSTANDING CHECK

10. How many do humans have?  Somatic cells = DIPLOID (2n) 46 chromosomes (23 pairs) 46 chromosomes (23 pairs) 22 pairs = Autosomes 22 pairs = Autosomes 1 pair = Sex chromosomes (X & Y) 1 pair = Sex chromosomes (X & Y) XX (female) vs. XY (male) XX (female) vs. XY (male)

11. Human Karyotype

13. UNDERSTANDING CHECK

14. How many do humans have?  Gametes = HAPLOID (n) Formed from germ cells Formed from germ cells 23 chromosomes (one of each) 23 chromosomes (one of each) Sperm + Egg = Zygote  YOU! Sperm + Egg = Zygote  YOU! 23 + 23 = 46 23 + 23 = 46

15. Haploid + Haploid = Diploid

16. Cell Cycle

17.  G1 – 1 st Growth – Routine functions  S – Synthesis – DNA Replication  G2 – 2 nd Growth – Prepare to Divide  M – Mitosis – Division of the Nucleus  C – Cytokinesis – Division of the Cytoplasm  MOVIE MOVIE

18. UNDERSTANDING CHECK

19. Cell Cycle  Numerous ways to control speed  Malfunction of cell cycle = cancer

20. Interphase  Includes the G1, S, & G2 phases  When the cell is not dividing or “at rest”  DNA is found unorganized in the nucleus

21. Interphase

22. Mitosis  Division of the nucleus to form 2 identical nuclei  Chromosome = 2 identical chromatids 2 identical chromatids (formed after replication) (formed after replication)

23. UNDERSTANDING CHECK

24. Mitosis  Prophase  Metaphase  Anaphase  Telophase  MOVIE 1 MOVIE 1 MOVIE 1  MOVIE 2 MOVIE 2 MOVIE 2

25. Prophase  Chromosomes become visible  Nuclear envelope dissolves  Spindle forms from centrioles

26. Prophase

27. Metaphase  Chromosomes line up along equator

28. Anaphase  Chromatids separate and reeled to opposite poles

29. Telophase  Nuclear envelope forms at each pole  Chromosomes uncoil  Spindle dissolves  Cytokinesis begins

30. Telophase

31. UNDERSTANDING CHECK

32. Cytokinesis  Division of the cytoplasm  Animal cells – pinch and split  Plant cells – forms cell plate down the center  MOVIE MOVIE

33. Meiosis  Formation of haploid gametes from one germ cell  Homologous chromosomes – chromosomes of similar size, shape, & genetic content

34. Meiosis  Meiosis I Prophase I Prophase I Metaphase I Metaphase I Anaphase I Anaphase I Telophase I Telophase I  Meiosis II Prophase II Metaphase II Anaphase II Telophase II

35. Prophase I  Homologous chromosomes pair up & crossing over occurs  Animation Animation  Allows genetic variation variation

36. Prophase I  Chromosomes become visible become visible  Nuclear env. breaks down breaks down  Spindle forms  Crossing over

37. Metaphase I  Pairs of homologous chromosomes move to equator of cell

38. Anaphase I  Homologous chromosomes reeled to opposite poles

39. Telophase I  Chromosomes gather at poles  Cytokinesis

40. Prophase II  New spindle forms

41. Metaphase II  Chromosomes line up on equator

42. Anaphase II  Chromatids reeled to opposite poles

43. Telophase II  Nuclear envelope forms  Cytokinesis

44. Meiosis

45. UNDERSTANDING CHECK

46. What can go wrong?  Nondisjunction – the chromosomes fail to separate during meiosis  Trisomy – individual has 3 of a particular chromosome  Down syndrome = trisomy 21

47. UNDERSTANDING CHECK

48. Meiosis in Males

49. Meiosis in Females