1 / 66

THE CELL CYCLE

THE CELL CYCLE. The Cell Cycle Events that occur in the life of a cell. Includes 3 major stages: Interphase Mitosis Cytokinesis. 1. Interphase (Cell is not dividing) G 1 Phase – carries out basic functions & performs specialized activities. duration is extremely variable

dung
Télécharger la présentation

THE CELL CYCLE

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. THE CELL CYCLE

  2. The Cell Cycle Events that occur in the life of a cell. Includes 3 major stages: • Interphase • Mitosis • Cytokinesis

  3. 1. Interphase (Cell is not dividing) • G1 Phase – carries out basic functions & performs specialized activities. • duration is extremely variable • contains restriction checkpoint ~ cell “decides” to: • divide • enter a quiescent phase (G0) • die

  4. 1. Interphase (Cell is not dividing) • G0 Phase – cell maintains specialized characteristics, but does not divide Ex. neurons & muscle cells

  5. 1. Interphase (Cell is not dividing) • S Phase – cell replicates chromosomes & synthesizes proteins • animal cells replicate centrioles as well

  6. 1. Interphase (Cell is not dividing) • G2 Phase - cell synthesizes additional proteins (ex. tubulin) & assembles/stores membrane material

  7. Mitosis (M phase) – Equal distribution of replicated genetic material. • Five steps: • Prophase • Prometaphase • Metaphase • Anaphase • Telophase

  8. Mitosis – Prophase • replicated chromosomes condense • centrosomes separate & migrate toward opposite sides of cell • mitotic spindle forms (microtubules grow out from centrosomes) • nucleolus disappears

  9. Mitosis – Prometaphase • nuclear membrane breaks down • spindle fibers attach to centromeres of chromosomes

  10. Mitosis – Metaphase • chromosomes are lined up single-file along equator of mitotic spindle

  11. Mitosis – Anaphase • Centromeres part, sister chromatids (now called chromosomes) separate • chromosomes move toward opposite poles

  12. Mitosis – Telophase • mitotic spindle breaks down • chromosomes decondense • nuclear membranes reform around two nuclei • nucleoli reappear

  13. Cytokinesis • Distribution of cytoplasm to daughter cells • begins during anaphase or telophase • differs in animal & plant cells

  14. Cytokinesis in animal cells • Cleavagefurrow (slight indentation) forms around equator of cell • Actin & myosin microfilaments act like a drawstring to pinch the cell in two • Usually an equal division

  15. Cytokinesis in plant cells • phragmoplast (microtubule structure) forms in cytoplasm & traps vesicles containing cell wall material • vesicles fuse, forming a cell plate across midline of cell • cell plate gives rise to two primary cell walls

  16. Review of the M-phase

  17. Review of the M-phase

  18. Review of the M-phase

  19. Review of the M-phase

  20. Review of the M-phase

  21. Review of the M-phase

  22. Review of the M-phase

  23. Review of the M-phase

  24. Review of the M-phase

  25. Review of the M-phase

  26. Does cytokinesis always accompany karyokinesis? Karyokinesis in the absence of cytokinesis results in a syncytium(mass of multinucleated cells).

  27. Control of the Cell Cycle Checkpoints - groups of interacting proteins that ensure cell cycle events occur in the correct sequence.

  28. Shortening of telomeres - loss of telomere DNA signals cell to stop dividing. Some cells produce telomerase(enzyme that continually adds telomere DNA).

  29. Contact Inhibition - healthy cells stop dividing when they come in contact with other cells.

  30. Hormones - stimulate cell division. Ex. Estrogen stimulates uterine cell division Growth factors - proteins that stimulate local cell division. Ex. Epidermal growth factor (EGF) stimulates epithelial cell division filling in new skin underneath a scab Interaction of kinases & cyclins - activate genes that stimulate cell division.

  31. B. Apoptosis Programmed cell death; part of normal development.

  32. Steps of Apoptosis:

  33. C. Cancer (loss of cell cycle control) Condition resulting from excess cell division or deficient apoptosis. Characteristics of Cancer Cells: • can divide uncontrollably & eternally • are heritable & transplantable • lack contact inhibition • readily metastasize • exhibit angiogenesis • exhibit genetic mutability

  34. Causes of Cancer: • Over-expression of oncogenes Oncogenes are genes that trigger limited cell division. • Inactivation of tumor suppressor genes Tumor suppressor genes prevent a cell from dividing or promote apoptosis.

  35. Normal functioning of oncogenes & tumor suppressor genes may be affected by environmental factors: • carcinogens • radiation • viruses • diet • exercise habits

  36. Meiosis - formation of gametes • Somatic cells – body cells • In contrast to mitosis (occurs in somatic cells), gametes (eggs or sperm) are produced only in gonads (ovaries or testes). • In the gonads, cells undergo a variation of cell division (meiosis) which yields four daughter cells, each with half the chromosomes of the parent. • In humans, meiosis reduces the number of chromosomes from 46 to 23 • Chromosomes #1 through 22 – autosomal • Chromosome #23 – sex

  37. Meiosis - formation of gametes • Fertilization fuses two gametes together and doubles the number of chromosomes to 46 again. • Organisms inherit single copy of each gene from each parent • These copies are segregated from each other during formation of the gametes • Homologous – corresponding male and female chromosomes

More Related