1. Cell Reproduction  Prokaryotes Bacteria  Eukaryotes Plants & animals

2. Prokaryotes  Lack a nucleus  Have a single chromosome  Reproduce by binary fission  Include bacteria

3. Steps in Binary Fission  Used by bacteria  Cells increase their cell mass slightly  the single, circular bacterial chromosome is replicated  Each cell divides into 2 daughter cells

4. 4

5. Binary Fission of Bacterial Cell

6. E. Coli Dividing by Binary Fission

7. Eukaryotes  Contain a nucleus & membrane bound organelles  Asexually reproduce cells by mitosis  Begins with 1 cells, ends with two cells that are genetically identical to each other and genetically identical to the original cell  Occurs in somatic cells  Since a human somatic cell has 46 chromosomes (23 pairs) how many chromosomes will a cell produced by mitosis have?

8. Cell Cycle The cycle from the beginning of the one cell until the time that one cell divides into two cells Mitosis is division of the nucleus Cytokinesis is division of cytoplasm and organelles Often the whole cell cycle is called mitosis, although this is not technically accurate

9. Purpose of Mitosis New cells for – Growth – Replacement (healing)

10. Cytokinesis  Occurs after chromosomes separate  Forms two, identical daughter cells

11. Cytokinesis Cell Plate Forming in Plant Cells

12. What is DNA like during cell division? DNA is always made of nucleotides with phosphate and sugar and nitrogenous bases, but what is the difference between DNA, genes, and chromosomes?

13. Chromosome, DNA, Gene demonstration

14. Chromosome- a DNA helix that is supercoiled, compacted, and organized around proteins; they appear as mitosis begins and uncoil into DNA and protein during Gene- a section of DNA that codes for a particular protein Chromatin- DNA and its associated proteins that are not coiled and compacted; form that DNA maintains during interphase DNA must be unwound to be able to be transcribed much like thread must be unwound to be used.

15. Details of Interphase

16. Cell Cycle  Interphase  G1 Phase  S Phase  G2 Phase  Mitosis -M Phase  Cytokinesis

17. Interphase – Resting Stage  Cells carrying on normal activities  Chromosomes aren’t visible, instead they are in the form of chromatin – a complex of protein and DNA  Cell metabolism is occurring  Centrioles (microtubule-organizing centers) replicate and one centriole moves to each pole.  Some sources make it the first stage of mitosis, some say it occurs before mitosis

18. Interphase - G1  First growth stage  Cell increases in size  Cell prepares to copy its DNA through the process of _____________ replication

19. Interphase – Synthesis  Replication - Copying of all of DNA’s instructions  Chromosomes duplicated

20. 20 Eukaryotic Chromosomes Chromosomes must be replicated before cell division. -Replicated chromsomes are connected to each other at their centromeres -sister chromatids: 2 copies of the chromosome within the replicated chromosome

21. 21

22. In body cells, chromosomes occur as pairs. Each set of chromosomes is a homologous pair; each member is a homologous chromosome or homologue. One member of each homologous pair is inherited from the male parent, the other member from the female parent. look alike, have the same length and centromere position, and have a similar banding pattern when stained. A location on one homologue contains genes for the same trait that occurs at this locus on the other homologue, although the genes may code for different variations of that trait (alleles). www.treachercollins.co.uk What are Homologous Chromosomes? (Mader 2007)

23. 23 Interphase Interphase is composed of: G 1 (gap phase 1) – time of cell growth S phase – synthesis of DNA (DNA replication) - 2 sister chromatids are produced G 2 (gap phase 2) – chromosomes condense

24. 24 Interphase Following S phase, the sister chromatids appear to share a centromere. In fact, the centromere has been replicated but the 2 centromeres are held together by cohesin proteins. Proteins of the kinetochore are attached to the centromere. Microtubules attach to the kinetochore.

25. 25 Chromatid Kinetochore microtubules Centromere region of chromosome Metaphase chromosome Cohesin proteins Kinetochore Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

26. Interphase

27. 27

28. Interphase - G2  Time between DNA synthesis & mitosis  Cell continues growing  Needed proteins produced

29. 29 Eukaryotic Cell Cycle The eukaryotic cell cycle has 5 main phases: 1. G 1 (gap phase 1) 2. S (synthesis) 3. G 2 (gap phase 2) 4. M (mitosis) 5. C (cytokinesis) The length of a complete cell cycle varies greatly among cell types. interphase

30. Details of Mitosis and Cytokinesis

31. Mitosis - M Phase  Cell growth & protein production stop  Cell’s energy used to make 2 daughter cells  Called mitosis (nuclear division)

32. Stages of Mitosis  Prophase  Metaphase  Anaphase  Telophase

33. Cells Undergoing Mitosis

34. Steps in Prophase  DNA coils tightly & becomes visible as chromosomes  Nuclear membrane disappears  Nuceolus disappears  Centrioles migrate to poles  Spindle begins to form

35. Prophase

36. Eukaryotic Chromosome

37. Human Chromosomes

38. Steps in Metaphase  Spindle fibers from centrioles attach to each chromosome  Cell preparing to separate its chromosomes  Cell aligns its chromosomes in the middle of the cell

39. Metaphase

40. Steps in Anaphase  Cell chromosomes are separated  Spindle fibers shorten so chromosomes pulled to ends of cell

41. Mitotic Spindle

42. Anaphase

43. Steps in Telophase  Separation of chromosomes completed  Cell Plate forms (plants)  Cleavage furrow forms(animals)  Nucleus & nucleolus reform  Chromosomes uncoil

44. Telophase Plant Animal

45. Cytokinesis  Occurs after chromosomes separate  Separation of cytoplasm and formation of new cells each with one of the new nuclei  Forms two, identical daughter cells

46. Cytokinesis Cell Plate Forming in Plant Cells

47. Cleavage in Animal Cell

48. 48 Eukaryotic Cell Cycle The eukaryotic cell cycle has 5 main phases: 1. G 1 (gap phase 1) 2. S (synthesis) 3. G 2 (gap phase 2) 4. M (mitosis) 5. C (cytokinesis) The length of a complete cell cycle varies greatly among cell types. interphase

50. Meiosis Creating Cells for Sexual Reproduction

51. Meiosis produces a haploid with only one set of chromosomes (reprented by N). Remember in somatic cells chromosomes come in pairs (2N), but meiosis produces haploid cells (gametes) that do not have pairs of chromosomes. They only have one set. Since human somatic cells have 46 (23 pair) of chromosomes, how many chromosomes are in a human gamete?

52. Definitions Diploid Cells- (2N)cells that have pairs of chromosomes. There are 2 of each chromosome in diploid cells. Haploid Cells- (N)cells that have only one of each chromosome. Haploid cells are used for sexual reproduction.

53. Meiosis is divided into Meiosis I and Meiosis II

54. Meiosis I

55. Prophase I Chromosomes are already copied Centrioles separate Nuclear membrane breaks down Crossing over occurs here

56. Crossing Over Synapsis- Homologous Pairs line up = Tetrad During synapsis the chromatids within a homologous pair may twist around each other and break off and attach to the other homologous pair = Crossing Over Results in exchange of genetic material between maternal and paternal chromosomes = genetic recombination

57. Metaphase I Chromosome pairs line up next to each other

58. Anaphase I Chromosome pairs split Sister chromatids stay connected

59. Telophase I Cell starts to divide in two Nuclear membranes start to form again

60. Meiosis II

61. Prophase II Cells have one set of sister chromatids Nuclear membrane breaks down Centrioles separate

62. Metaphase II Sister chromatids line up at the middle of the cell

63. Anaphase II Sister chromatids divide

64. Telophase II Cells start to split in two Each cell has one set of chromosomes—it is a haploid