1. CELL CYCLE
CHAPTER 12

2. Figure Mitosis

3. Figure 12.1a The functions of cell division: Reproduction

4. Figure 12.1b The functions of cell division: Growth and development

5. Figure 12.1c The functions of cell division: Tissue renewal

6. Figure 12.2 Eukaryotic chomosomes

7. Vocabulary
Chromatin – long, thin fibers of DNA wrapped around proteins
Chromosome – one long DNA molecule; condensed and clearly visible during cell division
Chromatid – two identical DNA molecules attached by a centromere (sister chromatids)

8. NEW VOCABULARY
Centrosome – microtubule organizing center which includes a pair of centrioles
Centrosomes replicate in interphase and move to opposite poles in prophase
Centromere – region where 2 chromatids are attached to one another
Kinetochore – specialized region of centromere where spindle fibers attach

9. Figure 12.3 Chromosome duplication and distribution during mitosis

10. CELL CYCLE Interphase G1 (first gap – cell grows)
S (DNA synthesis = chromosomes replicate)
G2 (second gap – cell grows)
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cell Cycle Animation
Mitosis Animation

11. Figure The cell cycle

12. Prophase Chromosomes visible
Centrosomes move towards opposite poles and begin making spindle fiber
Nuclear membrane, nucleus, and nucleolus disintegrate
Spindle fiber form and some attach to the kinetochores of the centromeres

13. Metaphase
Chromosomes line up at the middle of the cell

14. Figure 12.6 The mitotic spindle at metaphase

15. Figure 12.5 The stages of mitotic cell division in an animal cell: G2 phase; prophase; prometaphase

16. Anaphase
Sister chromatids are pulled apart and move toward opposite ends of the cell by the spindle fiber
Nonkinetochore spindle help elongate the cell
Cell plate begins to form in plant cells (immature cell wall)

17. Telophase and Cytokinesis
Events are opposite those of prophase
Nuclear membranes, nuclei, and nucleoli form in each new cell
Chromosomes unravel and become chromatin again
Spindle fibers disintegrate
Cytokinesis occurs – formation of cleavage

18. Figure The stages of mitotic cell division in an animal cell: metaphase; anaphase; telophase and cytokinesis.

19. Figure 12.5x Mitosis

20. Figure 12.8 Cytokinesis in animal and plant cells

21. Figure 12.9 Mitosis in a plant cell

22. Figure 12-09x Mitosis in an onion root

23. BINARY FISSION
Bacteria only have one chromosome so steps of mitosis are not needed
Bacteria replicate via binary fission
DNA replicates at a specific point (origin of replication)

24. Figure 12.10 Bacterial cell division (binary fission) (Layer 3)

25. Evolution of Mitosis
Prokaryotic and eukaryotic cell division share some similar proteins that are involved in cell division
Possible intermediates:
Current examples in some protists
Nuclear envelopes remain intact and replicated chromosomes attach to envelope
As nucleus elongates, chromosome separate
Spindle forms inside nucleus
Prokaryotic proteins also involved in tubulin and actin proteins

26. REGULATION OF CELL CYCLE
Checkpoints – critical points in cell cycle where process can stop or go ahead according to signals
Kinases – enzymes that can activate or inactivate something via phosphorylation

27. Figure 12.13 Mechanical analogy for the cell cycle control system

28. Restriction point or G1 checkpoint – the most critical of checkpoints
During G1, if signaled to proceed then cell usually completes cell cycle and divides
If no signal to proceed, cell goes into nondividing state, G0
Most cells are in G0
Go signal means enter S and replicate DNA

29. Cyclin is a protein that activates kinases that are called cyclin-dependent kinases or Cdks
MPF (maturation promoting factor) – combination of Cdks and cyclin

30. Cyclins accumulate during G2 and associate with Cdk’s to make MPF
MPF initiates mitosis at G2 checkpoint by phosphorylating various proteins
Nuclear membrane is phosphorylated and this causes it to break down
Proteolytic enzymes break down MPF which helps end mitosis

31. Figure 12.14 Molecular control of the cell cycle at the G2 checkpoint

32. M Phase Checkpoint M phase (metaphase checkpoint)
Kinetochores not attached yet to spindle send delay signals to prevent anaphase from starting too early.
Why must the cell wait for all of the chromosomes to line up in the middle of metaphase before proceeding to anaphase?

33. OTHER SIGNALS
A signal that delays anaphase so that right number of chromosomes end up in each new cell
Growth factors – external signals that can stimulate cell division

34. Density-dependent inhibition – cells stop dividing when crowded
Anchorage-dependent – most animal cells must be attach to substratum

35. Figure 12.16 Density-dependent inhibition of cell division

36. CANCER Cancer – cells that divide excessively and invade other tissues
Metastasis – spread of cancer cells
Tumor – mass of abnormal cells
Benign – cells stay “put”, not cancer
Malignant – cells move (metastasis), cancer

37. Figure 12.17 The growth and metastasis of a malignant breast tumor

38. Figure 12-17x1 Breast cancer cell

39. Figure 12-17x2 Mammogram: normal (left) and cancerous (right)

40. MEIOSIS
CHAPTER 13

41. REPRODUCTION
Asexual reproduction – single parent passes on all of its genes to its offspring
Sexual reproduction – two parents give rise to offspring that have a combination of genes inherited from two parents

42. Figure 13.1 The asexual reproduction of a hydra

43. VOCABULARY Karyotype – picture of an organisms chromosomes
Homologous chromosomes – pair of similar chromosomes
Haploid – single chromosome set (n=23 for humans)
Diploid – two sets of chromosomes (2n=46 for humans)
Zygote – fertilized egg

44. Fertilization or syngamy – fusion of sperm and egg
Somatic cell – body cells
Gametes – sex cells
Sex chromosomes – determine gender
Autosomes – all other chromosomes
Sister chromatids – copies of same chromosome

45. HUMAN FEMALE

46. HUMAN MALE

47. Figure 13.x1 SEM of sea urchin sperm fertilizing egg

48. Figure 13.4 The human life cycle

49. MEIOSIS A process that halves the chromosome number
Mitosis vs. Meiosis
Genetic recombination

50. Figure 13.6 Overview of meiosis

51. Figure Meiosis I

52. Figure Meiosis II

53. Figure 13.8 Mitosis vs. Meiosis

54. Figure 13.8 Mitosis vs. Meiosis

55. Figure 13.9 Different possible sex cells (Independent Assortment of Chromosomes)

56. MORE GENETIC POSSIBILITIES
Synapsis – pairing of homologous chromosomes in prophase I
Chiasmata or crossing over– when homologous portions of two nonsister chromatids trade place

57. Figure 13.10 Crossing over during meiosis