cell cycle.pptx for 1st semester Physiology

Cell cycle description for 1 st semester Physiology

1. OVERVIEW OF THE CELL CYCLE INTRACELLULAR CONTROL OF THE CELL CYCLE EXTRACELLULAR CONTROL OF CELL DIVISION AND CELL GROWTH fatimaArivera

2. Flow of discussion 1.Overview of the cell cycle G1phase S phase Interphase G2 phase Mitosis phase * prophase, metaphase, anaphase, telophase, * cytokinesis Meiosis 2.Intracellular Control of the Cell Cycle Positive: Cyclin - dependent kinase & Cyclins Negative: Rb & p53 3. Extracellular Control of the Cell Cycle Mitogens Growth factors Survival factors fatimaArivera

3. Overview: The Key Roles of Cell Division The ability of organisms to reproduce best distinguishes living things from non-living matter. The continuity of life is based upon the reproduction of cells, or cell division. Cell division is integral part of cell cycle.

4. Overview of the cell cycle fatimaArivera

5. Cell cycle: interphase Interphase includes: G 1 Phase: S Phase: G 2 Phase: fatimaArivera

6. INTERPHASE: G1 PHASE Recovery from previous division Cell doubles its organelles Cell grows in size Accumulates raw materials for DNA synthesis (DNA replication) fatimaArivera

7. INTERPHASE: S PHASE DNA replication Proteins associated with DNA are synthesized fatimaArivera

8. INTERPHASE: G2 PHASE Between DNA replication and onset of mitosis Cell synthesizes proteins necessary for division fatimaArivera

9. Cell cycle: mitosis phase Mitosis phase includes: Mitosis ( karyokinesis ) Nuclear division Daughter chromosomes distributed to two daughter nuclei Cytokinesis Cytoplasm division Results in two genetically identical daughter cells fatimaArivera

10. Cell cycle: mitosis phasE fatimaArivera

11. SIGNIFICANCE OF MITOSIS Permits growth and repair. In plants it retains the ability to divide throughout the life of the plant In mammals, mitosis is necessary: Fertilized egg becomes an embryo Embryo becomes a fetus Allows a cut to heal or a broken bone to mend fatimaArivera

12. Mitosis phase: prophase What’s happening? Chromatin condenses. Centrosomes separate, moving to opposite ends of the nucleus The centrosomes start to form a framework used to separate the two sister chromatids called the mitotic spindle, that is made of microtubules Nucleolus disappears Nuclear envelope disintegrates What the cell looks like ? fatimaArivera

13. Mitosis phase: prometaphase What’s happening? Nuclear envelope fragments Chromosomes become more condensed A kinetochore is formed at the centromere , the point where the sister chromatids are attached Microtubules attach at the kinetochores What the cell looks like ? fatimaArivera

14. Mitosis phase: metaphase What’s happening? Chromosomes align on an axis called the metaphase plate Note: the spindle consists of microtubules, one attached to each chromosome What the cell looks like? fatimaArivera

15. Mitosis phase: anaphase What’s happening? Each centromere splits making two chromatids free Each chromatid moves toward a pole Cell begins to elongate , caused by microtubules not associated with the kinetochore What the cell looks like? fatimaArivera

16. Mitosis phase: telophase What’s happening? Formation of nuclear membrane and nucleolus Short and thick chromosomes begin to elongate to form long and thin chromatin Formation of the cleavage furrow - a shallow groove in the cell near the old metaphase plate Cytokinesis = division of the cytoplasm What the cell looks like? fatimaArivera

17. Results of mitosis fatimaArivera Two daughter nuclei Each with same chromosome number as parent cell ( 2n) Genetically identical to each other and the parent cell

18. meiosis Formation of Gametes (Eggs & Sperm) Called Reduction- division Preceded by interphase which includes chromosome replication Two meiotic divisions Meiosis I and Meiosis II Original cell is diploid (2n) Four daughter cells produced that are haploid (n) fatimaArivera

19. SIGNIFICANCE OF MEIOSIS Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote fatimaArivera

20. SIGNIFICANCE OF MEIOSIS Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number from mom from dad child meiosis reduces genetic content T oo much! The right number! fatimaArivera

21. MEIOSIS i: PROPHASE i Prophase I is further subdivided into periods known as Leptotena Zygotena Pachytena Diplotena Diakinesis fatimaArivera

22. A physical exchange of chromosome pieces PROPHASE I fatimaArivera

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

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

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

26. MEIOSIS II: Prophase II Nuclear envelope fragments. Spindle forms. fatimaArivera

27. MEIOSIS II: Metaphase II Chromosomes align along equator of cell . fatimaArivera

28. MEIOSIS II: Anaphase II Sister chromatids separate and move to opposite poles . Equator Pole fatimaArivera

29. MEIOSIS II: Telophase II Nuclear envelope assembles. Chromosomes decondense . Spindle disappears. Cytokinesis divides cell into two. fatimaArivera

30. Results of Meiosis Four haploid cells with one copy of each chromosome fatimaArivera

31. SUMMARY OF MEIOSIS I fatimaArivera Nucleus Spindle fibers Nuclear envelope EARLY PROPHASE I LATE PROPHASE I METAPHASE I ANAPHASE I TELOPHASE I & CYTOKINESIS

32. SUMMARY OF MEIOSIS II Prophase II Metaphase II Anaphase II Telophase II 4 I Undentical haploid cells fatimaArivera

33. Mitosis Meiosis Number of divisions 1 2 Number of daughter cells 2 4 Genetically identical? Yes No Chromosome # Same as parent Half of parent Where Somatic cells Germ cells When Throughout life At sexual maturity Role Growth and repair Sexual reproduction Comparison of Divisions fatimaArivera

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35. Flow of discussion 1.Overview of the cell cycle G1phase S phase Interphase G2 phase Mitosis phase * prophase, metaphase, anaphase, telophase, * cytokinesis Meiosis 2.Intracellular Control of the Cell Cycle Positive: Cyclin - dependent kinase & Cyclins Negative: Rb & p53 3. Extracellular Control of the Cell Cycle Mitogens Growth factors Survival factors fatimaArivera

36. Intracellular control of the cell cycle The cell cycle is controlled by regulator molecules that either: promote the process (positive) stop it from progressing (negative) fatimaArivera

37. Positive: Cdks & Cyclins Cyclins The regulatory subunits of the protein kinases that control the cell cycle Cyclin -Dependent Kinases ( Cdks ) The catalytic subunits of the protein kinases Must be associated with a cyclin in order to be activated fatimaArivera

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39. Negative: Rb & p53 Tumor suppressor genes Tumor suppressor gene codes for a signaling protein in an inhibitory pathway. If a tumor suppressor gene mutates, the end result can be active cell division. fatimaArivera

40. Negative: Rb & p53 Retinoblastoma protein( Rb ) prevents cell moving into S phase by binding to a transcription factor When Rb is phosphorylated it cannot bind so cell can move into S phase p53 prevents damaged from dividing (by inhibiting Rb pathway) fatimaArivera

41. Retinoblastoma protein ( Rb ) fatimaArivera Rb halts the cell cycle by binding E2F. Rb releases its hold on E2F in response to cell growth to advance the cell cycle. group of tumor-suppressor proteins

42. p53 p53 protein halts cell division if it detects damaged DNA options: stimulates repair enzymes to fix DNA forces cell into G resting stage keeps cell in G 1 arrest causes apoptosis of damaged cell ALL cancers have to shut down p53 activity Cancer is essentially a failure of cell division control fatimaArivera p53 is the Cell Cycle Enforcer

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44. Major molecule players in the cell cycle control fatimaArivera Cyclin -dependent kinases ( Cdks ) Cyclins Cdk-cyclin complex P regulatory proteins phosphorylates cellular proteins triggers passage through different stages of cell cycle

45. Generic cell cycle checkpoints fatimaArivera Is environment favorable? Is environment favorable? Are all DNA replicated? Are all chromosomes attached to the spindle?

46. G1 S G2 M G1 Checkpoint G2 Checkpoint M Checkpoint G1 Cdk G1 Cyclin P Active G1 Cdk-Cyclin Growth factors Nutritional state of cell Size of cell Degraded G1 Cyclin Mitotic Cdk Mitotic Cyclin P Active Mitotic Cdk-Cyclin (MPF) Replication completed DNA integrity APC Chromosomes attached at metaphase plate Degraded Mitotic Cyclin Control of the Cell Cycle

47. Flow of discussion 1.Overview of the cell cycle G1phase S phase Interphase G2 phase Mitosis phase * prophase, metaphase, anaphase, telophase, * cytokinesis Meiosis 2.Intracellular Control of the Cell Cycle Positive: Cyclin - dependent kinase & Cyclins Negative: Rb & p53 3. Extracellular Control of the Cell Cycle Mitogens Growth factors Survival factors fatimaArivera

48. Extracellular Control of the Cell Division and Cell Growth What regulates cell size and cell number? Regulated by extracellular signals Mitogens stimulate cell division (PDGF) Growth factors stimulate cell growth Survival Factors inhibit apoptosis fatimaArivera

49. MITOGEN: Platelet Derived Growth Factor PDGF is released by platelets in at the site of a wound

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51. GROWTH FACTORS fatimaArivera A signal transduction through phosphatidyl inositol pathway Kinase cascade leads to increased translation Some factors stimulate both growth and cell cycle progression

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54. protein signals released by body cells that stimulate other cells to divide density-dependent inhibition crowded cells stop dividing each cell binds a bit of growth factor not enough activator left to trigger division in any one cell anchorage dependence to divide cells must be attached to a substrate “ touch sensor ” receptors GROWTH FACTORS

55. Normal cells need both mitogens and “anchorage”- to enter a new cell cycle

56. Nerve growth factors can influence both rate and direction of growth

57. SURVIVAL FACTOR: Myostatin Myostatins are inhibitory factors that inhibit the proliferation of myoblast that fuse to form skeletal muscle cells. Myostatin Mutants decrease apoptosis in muscle tissue

58. THANK YOU! fatimaArivera