cell division - mitosis


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cell division - mitosis

  1. 1. Edited by: Hasimah Azit
  2. 2. CELL DI VI SI ON FUNCTI ONS I S t o : Produce new cells for: reproduction – gamete growth – new cells and repair – replace dead cells
  3. 3. Basi c def i ni t i ons  gene - basic unit of heredity; codes for a specific trait  somatic cell - all body cells except reproductive cells  gamete - reproductive cells (i.e. sperm & eggs)  chromosome - elongate cellular structure composed of DNA and protein
  4. 4. Basic definitions  diploid (2n) - cellular condition where each chromosome type is represented by two homologous chromosomes  haploid (n) - cellular condition where each chromosome type is represented by only one chromosome  chromatid - one of two duplicated chromosomes connected at the centromere  centromere - region of chromosome where microtubules attach during mitosis and meiosis
  5. 5. Ce l l di vi s i on i nvol ve s  the distribution of identical genetic material, DNA  to two daughter’s cells. 2n two identical daughter 2n cells 2n
  6. 6. The Cell Cycle
  7. 7. Ce l l Cyc l e  The dividing and non-dividing stages in the life of a cell.  Phases: 1. Interphase: growth and DNA replication Interphase 2. Prophase 3. Metaphase 4. Anaphase Mitotic division 5. Telophase 6. Cytokinesis – cytoplasm divided
  8. 8. I nt e r phas e 1. G1 (gap) phase: a. grow into matured size and protein is synthesized b. most cell are arrested in this phase. phase 2. S phase: a. DNA replication takes place. 3. G2 (gap) phase: a. Cellular growth and energy and organelles preparation for M phase. phase
  9. 9. M t os i s i The form of cell division by which a somatic cell duplicates. Mitosis is asexual reproduction. Cell division is the continuation of life based on the reproduction of cells.
  10. 10. Mitosis division mitosis - nuclear/chemical events resulting in two daughter nuclei which have identical genetic material to each other and to the mother cell cytokinesis - division of the cytoplasm.
  11. 11. Look at the section through the tip of an onion root tip and try to recognize: * dividing cells – mitotic cells * elongated cells
  12. 12. Onion root tip Elongated cells Mitotic cells
  13. 13. I nt e r phas e Nucleus and nucleolus visible. chromatin Nuclear membrane cell membrane nucleolus
  14. 14.  A chromosome is made up of a DNA  Chromatin is a long, thin fiber that is folded and coiled (invisible). chromosome
  15. 15. Duplication of chromosome – from single strand to double strand
  16. 16. Chr om om r e pl i c at i on os e  A replicated chromosome consist of two strands of identical chromosomal material called chromatids (sister chromatids). chromatids chromosome S phase: chromosomes replicate chromatid chromosome chromatid centromere
  17. 17. Chromatid  A chromatid is a chromatid as long as it is held in association with a sister chromatid at the centromere. centromere centromere chromatid chromosome chromatid
  18. 18. Pr ophas e  Longest phase  Nucleolus disappears  Chromatin material condenses into chromosomes, chromosomes consisting of two sister chromatids. chromatids
  19. 19. Pr ophas e  Centrioles move apart (not found in plants).  Spindle fibers form and attach from centrioles to centromeres  Nuclear envelope fragments and disappears.
  20. 20. Pr ophas e early prophase late prophase centrioles spindle fibers aster fibers nuclear envelope disappearing centromere
  21. 21. Find the stages in the picture below
  22. 22. M t aphas e e  Shortest phase  Centrioles are at opposite ends of the cell and attached with aster fibers. fibers  Chromosomes move to the metaphase plate (equatorial plate - center of cell).
  23. 23. M t aphas e e centrioles aster fibers spindle fibers metaphase plate
  24. 24. Anaphas e  Centromeres uncouple and spindle fibers shorten.  Sister chromatids separate and move apart.  After separation, chromatids are now considered chromosomes. chromosomes
  25. 25. Anaphas e During this phase, the cell contains twice the normal number of chromosomes. chromosomes Cell begins to elongate. elongate At the end, there are equal numbers of chromosomes at the poles.
  26. 26. Anaphas e No longer sister chromatids, now chromosomes chromatids aster fibers spindle fibers centrioles
  27. 27. Te l ophas e  Cleavage furrow develops in animal cells (Cytokinesis begins).  Cell plate develops in plants (no cleavage furrows in plants).  Nucleolus reappears. cell plate
  28. 28. Te l ophas e  Nuclear membrane reappears.  Chromosomes uncoil.  In the end, two genetically identical nuclei (karyokinesis completed) are present.
  29. 29. Te l ophas e cleavage furrow (cytokinesis) nuclear membrane reforming nucleolus reappears
  30. 30. Cyt oki ne s i s  Cytoplasmic division  Cell plate complete in plants  In the end, two separate daughter cells produced with single nucleus. cell plate
  31. 31. Que s t i on :  A cell containing 20 chromosomes at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes each? each
  32. 32. Ans we r : 20 chromosomes
  33. 33. Que s t i on :  A cell containing 40 chromatids at the beginning of mitosis would, at its completion, produce cells containing how many chromosomes each? each
  34. 34. Ans we r : 20 chromosomes
  35. 35. What i s cancer ?  A cancer cell is a cell that grows out of control.  Unlike normal cells, cancer cells ignore signals to stop dividing, to specialize, or to die and be shed.  Growing in an uncontrollable manner and unable to recognize its own natural boundary, the cancer cells may spread to areas of the body where they do not belong.
  36. 36. White blood cells attack the cancerous cell!
  37. 37. Fi nd your sel f :  How the cancerous cells look like?  How these cells affect the health?  How these cells spread?  What causes the cancer in human?
  38. 38. Websi t e f or you t o vi si t:  http://www.cellsalive.com/mitosis.htm  http://www.biology.arizona.edu/Cell_bio/tutorials  http://www.accessexcellence.org/RC/VL/GG/mito  http://training.seer.cancer.gov/module_cancer_di