1. 1 Cellular Division

2. 2 I. Cell Division All cells are derived from pre- existing cells All cells are derived from pre- existing cells New cells are produced for growth and to replace damaged or old cells New cells are produced for growth and to replace damaged or old cells

3. 3 A.Keeping Cells Identical A.Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA

4. 4 B.DNA Replication DNA must be copied or replicated before cell division so each new cell will have a copy DNA must be copied or replicated before cell division so each new cell will have a copy Original DNA strand strand Two new, identical DNA strands

5. 5 Identical Daughter Cells Parent Cell Two identical daughter cells

6. 6 Prokaryote cell division Binary Fission

7. 7 C. Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells (humans have 46) Most eukaryotes have between 10 and 50 chromosomes in their body cells (humans have 46) Each chromosome is made of a single, tightly coiled DNA molecule Each chromosome is made of a single, tightly coiled DNA molecule

8. 8 Chromosomes Chromatin

9. 9 Chromosome structure Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids

10. 10 The Cell Cycle in Eukaryotic Cells

11. 11 II. Eukaryote Cell Cycle II. Eukaryote Cell Cycle A. Interphase – longest phase (3 parts) -G 1 - primary growth phase of cell -S – synthesis; DNA replicated -G 2 - secondary growth phase B. Mitosis (division of nucleus) -Prophase, Metaphase, Anaphase, Telophase C. Cytokinesis (division of cytoplasm)

12. 12 Cell Cycle

13. 13 Mitosis (4 Phases)

14. 14 Mitosis Division of the nucleus Division of the nucleus Eukaryotes only Eukaryotes only Has four stages Has four stages Doesn’t occur in some cells such as brain cells Doesn’t occur in some cells such as brain cells

15. 15 Four Mitotic Stages 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

16. 16 1.Prophase Chromatin in nucleus condenses to form visible chromosomes Chromatin in nucleus condenses to form visible chromosomes Spindle fibers form cytoskeleton or centrioles (animal) Spindle fibers form cytoskeleton or centrioles (animal) Nuclear membrane & nucleolus are broken down and disappear Nuclear membrane & nucleolus are broken down and disappear Chromosomes Nucleolus Cytoplasm Nuclear Membrane

17. 17 Late Prophase Nucleus & Nucleolus have disintegrated Chromosomes

18. 18 2. Metaphase Chromosomes, attached to the spindle fibers, Chromosomes, attached to the spindle fibers, Chromosomes are now lined up at the equator Chromosomes are now lined up at the equator Pole of the Cell Equator of Cell

19. 19 Metaphase Chromosomes lined at the Equator Spindle Fibers

20. 20 3. Anaphase Sister chromatids are pulled apart to opposite poles of the cell Sister chromatids are pulled apart to opposite poles of the cell

21. 21 Anaphase Sister Chromatids being separated

22. 22 4. Telophase Spindle fibers disappears Spindle fibers disappears Nuclear envelope forms around each set of sister chromatids Nuclear envelope forms around each set of sister chromatids Nucleolus reappears Nucleolus reappears Chromosomes uncoil back to chromatin Chromosomes uncoil back to chromatin CYTOKINESIS occurs after telophase CYTOKINESIS occurs after telophase

23. 23 Telophase

24. 24 Cytokinesis Division of the cytoplasm Division of the cytoplasm Division of cell into two, identical halves called daughter cells Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell In animal cells, cleavage furrow forms to split cell

25. 25 Cytokinesis Cleavage furrow in animal cell Cell plate in plant cell

26. 26 Daughter Cells of Mitosis Have the same number of chromosomes as each other and as the parent cell from which they were formed Have the same number of chromosomes as each other and as the parent cell from which they were formed Identical to each other, but smaller than parent cell Identical to each other, but smaller than parent cell Must grow in size to become mature cells (G 1 of Interphase) Must grow in size to become mature cells (G 1 of Interphase)

27. 27 Interphase Prophase Metaphase Anaphase Telophase Name the Mitotic Stages: Name this?

28. 28 Mitosis in Onion Root Tips Do you see any stages of mitosis?

29. 29 Test Yourself over Mitosis

30. 30 Mitosis Animation Name each stage as you see it occur

31. 31 Mitosis Quiz

32. 32 Mitosis Quiz

33. 33 Name the Stages of Mitosis: Interphase Early prophase Mid-Prophase Late Prophase Metaphase Late Anaphase Early Anaphase Early Telophase, Begin cytokinesis Late telophase, Advanced cytokinesis

34. 34 III.Uncontrolled Mitosis If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors Can be caused by pollution, UV exposure Can be caused by pollution, UV exposure Cancer can be treated by chemotherapy, and radiation Cancer can be treated by chemotherapy, and radiation Cancer cells Skin Cancer

35. 35 Eukaryotic Cell Division Used for growth and repair Used for growth and repair Produce two new cells identical to the original cell Produce two new cells identical to the original cell Cells are diploid (2n) Cells are diploid (2n) Chromosomes during Metaphase of mitosis ProphaseMetaphase Anaphase Telophase Cytokinesis

36. 36 Types of Chromosomes Sex Chromosomes –Determine the sex or gender of an organism –Contain other genes for other characteristics –XX=girl, XY=boy Autosomes - All other chromosomes -Homologous Chromosomes - copies of each autosome (1 from each parent) - same size, shape and carry the same genes for the traits

37. 37 Karyotype A picture of the chromosomes from a human cell arranged in pairs by size A picture of the chromosomes from a human cell arranged in pairs by size First 22 pairs are called autosomes First 22 pairs are called autosomes Last pair are the sex chromosomes Last pair are the sex chromosomes XX female or XY male XX female or XY male

38. 38 Boy or Girl? Y - Chromosome X - Chromosome The Y Chromosome Decides

39. 39 Haploid vs Diploid Cells Diploid (2n) –Most cells in the body –Two sets of chromosomes Homologous chromosomes and two sex chromosomes Example: Humans have 46 chromosomes (22 homologous and 2 sex chromosomes Haploid (1n) –Sex cells (sperm and eggs) –One set of chromosomes (1/2 the number of chromosomes)

40. 40 Meiosis Formation of Gametes (Eggs & Sperm)

41. 41 Facts About Meiosis Occur after interphase which includes chromosome replication Occur after interphase which includes chromosome replication Two meiotic divisions Two meiotic divisions Meiosis I and Meiosis II Meiosis I and Meiosis II Original cell is diploid (2n) Original cell is diploid (2n) Four daughter cells produced are haploid (1n) Four daughter cells produced are haploid (1n)

42. 42 Facts About Meiosis Daughter cells contain half the number of chromosomes as the original cell Daughter cells contain half the number of chromosomes as the original cell Produces gametes (eggs & sperm) Produces gametes (eggs & sperm) Occurs in the testes of males (Spermatogenesis) Occurs in the testes of males (Spermatogenesis) Occurs in the ovaries of females (Oogenesis) Occurs in the ovaries of females (Oogenesis)

43. 43 Why Do we Need Meiosis? It is the fundamental basis of sexual reproduction It is the fundamental basis of sexual reproduction Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote

44. 44 Fertilization – “Putting it all together” 1n =3 2n = 6

45. 45 Meiosis Forms Haploid Gametes Meiosis must reduce the chromosome number by half Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number Fertilization then restores the 2n number from momfrom dadchild meiosis reduces genetic content too much! The right number!

46. 46 Meiosis I: Reduction Division Nucleus Spindlefibers Nuclearenvelope Early Prophase I Late Prophase I Metaphase I Anaphase I Telophase I (diploid)

47. 47 Prophase I Early prophase Homologs pair up Homologs pair up Crossing over occurs Crossing over occurs Late prophase Chromosomes condense Chromosomes condense Spindle forms Spindle forms Nuclear envelope fragments Nuclear envelope fragments

48. 48 Homologous chromosomes in a tetrad cross over each other Homologous chromosomes in a tetrad cross over each other Pieces of chromosomes or genes are exchanged Pieces of chromosomes or genes are exchanged Produces Genetic recombination in the offspring Produces Genetic recombination in the offspring Crossing-Over in Prophase I

49. 49 Metaphase I Homologous pairs of chromosomes align along the equator of the cell

50. 50 Anaphase I Homologs separate and move to opposite poles. Sister chromatids remain attached at their centromeres attached at their centromeres.

51. 51 Telophase I Nuclear envelopes reassemble. Spindle disappears. Cytokinesis divides cell into two.

52. 52 Meiosis II: Reducing Chromosome Number Prophase II Metaphase II Anaphase II Telophase II 4 Identical haploid cells

53. 53 Prophase II Nuclear envelope (if it reformed) disappears. Spindle forms.

54. 54 Metaphase II Chromosomes align along equator of cell.

55. 55 Anaphase II Sister chromatids separate and move to opposite poles Sister chromatids separate and move to opposite poles. Equator Pole

56. 56 Telophase II Nuclear envelope assembles. Chromosomes decondense. Spindle disappears. Cytokinesis divides cell into two.

57. 57 Results of Meiosis Gametes (egg & sperm) form Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome Four haploid cells with one copy of each chromosome One allele of each gene One allele of each gene Different combinations of alleles for different genes along the chromosome Different combinations of alleles for different genes along the chromosome

58. 58 Gametogenesis Oogenesis or Spermatogenesis

59. 59 Spermatogenesis Occurs in the testes Occurs in the testes Two divisions (Meiosis) produce 4 spermatids Two divisions (Meiosis) produce 4 spermatids Spermatids mature into sperm Spermatids mature into sperm Men produce about 250,000,000 sperm per day Men produce about 250,000,000 sperm per day

60. 60 Oogenesis Occurs in the ovaries Occurs in the ovaries Two divisions produce 3 polar bodies that die and 1 egg Two divisions produce 3 polar bodies that die and 1 egg Polar bodies die because of unequal division of cytoplasm Polar bodies die because of unequal division of cytoplasm Immature egg called oocyte Immature egg called oocyte Starting at puberty, one oocyte matures into an ovum (egg) every 28 days Starting at puberty, one oocyte matures into an ovum (egg) every 28 days

61. 61 Comparing Mitosis and Meiosis

62. 62 MitosisMeiosis Number of divisions 12 Number of daughter cells 24 Genetically identical? YesNo Chromosome # Same as parent (2n) Half of parent (1n) Where Somatic cells (Body cells) Germ cells (Sex cells) When Throughout life At sexual maturity Role Growth and repair Sexual reproduction Comparison of Divisions