Cell division


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  • Interphase (90% of cycle)
    • G1 phase~ growth
    • S phase~ synthesis of DNA
    • G2 phase~ preparation for cell division
    Mitotic phase
    • Mitosis~ nuclear division
    • Cytokinesis~ cytoplasm division
  • Cell division

    1. 1. Cell Division Mitosis- Cell reproduction
    2. 2. Learning Objectives • • • • The cell cycle and its phases. The cell division “mitosis”. Cell cycle control system. The different abnormalities of cell cycle (cancer). • DNA structure and DNA replication .
    3. 3. Key Words • • • • • Chromosome chromatin centriole & centrosome centromere & kinetochore chromatid Bayan Al-Ghadeer Dalal Al-Anazi
    4. 4. chromosome A chromosome is a long, continuous piece of DNA which contains the genetic information for a cell. Bayan Al-Ghadeer Dalal Al-Anazi
    5. 5. chromatin Chromatin is the building block for a chromosome. It consists of DNA and proteins. Bayan Al-Ghadeer Dalal Al-Anazi
    6. 6. Centriole & centrosome A centriole is a barrel microtubule structure. Two centrioles arrange themselves perpendicularly to form a centrosome. Bayan Al-Ghadeer Dalal Al-Anazi
    7. 7. centromere & kinetochore • The centromere is constricted region of the chromosomes that holds the sister chromatids together, the site where kinetochore forms. • The kinetochore is a complex protein containing structure to which microtubules attach. Bayan Al-Ghadeer Dalal Al-Anazi
    8. 8. chromatid Is a one strand of the chromosome after it has duplicated for cellular division. The two chromatids are called “sister chromatids” and will eventually split and move to opposite ends of the cell. Bayan Al-Ghadeer Sister chromatids Dalal Al-Anazi
    9. 9. Ready? Let’s begin Bayan Al-Ghadeer Dalal Al-Anazi
    10. 10. Cell division Bayan Al-Ghadeer Dalal Al-Anazi
    11. 11. Why do cells divide? •Growth •Repair and replace dead cells •asexual reproduction Bayan Al-Ghadeer Dalal Al-Anazi
    12. 12. THE CELL CYCLE ______________________ _
    13. 13. • Define cell cycle: the cell cycle is the sequence of growth and division of a cell. It consists of three major phases: o interphase o mitosis o cytokinesis. • Cell division results in two cells that are both identical to the parent cell. Bayan Al-Ghadeer Dalal Al-Anazi
    14. 14. Interphase Estimated (90% of cycle) 3 phases •G1 phase •S phase •G2 phase Bayan Al-Ghadeer Dalal Al-Anazi
    15. 15. G1 phase • Growth of cell. • Dupliction of organelles. • Synthisis of proteins. Bayan Al-Ghadeer Dalal Al-Anazi
    16. 16. S phase • DNA synthesis occurs • DNA replication results in duplicated chromosomes • centrosome cycle Bayan Al-Ghadeer Dalal Al-Anazi
    17. 17. G2 phase • Cell continues to grow and if a problem occurs in DNA replication, it will be repaired. • Cell will prepare for mitosis. • cell synthesizes proteins needed for cell division Bayan Al-Ghadeer Dalal Al-Anazi
    18. 18. M phase Estimated (10% of cycle) Includes 2 parts : 1)Mitosis •Prophase •Promataphase •Metaphase •Anaphase •Telophase 2) Cytokinesis Bayan Al-Ghadeer Dalal Al-Anazi
    19. 19. Mitosis • is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter cells. Bayan Al-Ghadeer Dalal Al-Anazi
    20. 20. Prophase Duration (15 min) • Chromosomes condense (get thicker) and coil, they become visible under light microscope. • The two sister chromatids of each chromosomes attach at a point called centromere. • Spindle fibers begin to form from two centrosome, and they will start moving apart. Bayan Al-Ghadeer Dalal Al-Anazi
    21. 21. Prometaphase Duration (15 min) • The nuclear membrane disappears. • Kinetochores will get attached to the centromere. • The spindle fibers become attached to the kinetochore. Bayan Al-Ghadeer Dalal Al-Anazi
    22. 22. Metaphase Duration (20 min) • Chromosomes reach their most highly condensed state. • The spindle fibers begin to contract to the centromeres of the chromosomes, which are now arranged along the middle of the spindle. Bayan Al-Ghadeer Dalal Al-Anazi
    23. 23. Anaphase: Duration (3 min) • The centromere of each chromosome splits, allowing the sister chromatids to separate. • The chromatids are then pulled by the spindle fibers toward opposite sides of the cell. • The two sets of chromosomes are identical. • Cleavage furrow starts to form. Bayan Al-Ghadeer Dalal Al-Anazi
    24. 24. Telophase: Duration (10 min) • New nuclear membranes are formed around each of the two sets of 46 chromosomes. • The spindle fibers disappear. • Chromosomes become thinner. • Cytoplasm starts dividing by contractile ring. • At the end, we will have two diploid daughter cells, which are identical. Bayan Al-Ghadeer Dalal Al-Anazi
    25. 25. Cytokinesis • • the division of the cytoplasm and organelles Begin in anaphase and completed by the end of telophase . Bayan Al-Ghadeer Dalal Al-Anazi
    26. 26. Summary • o o o Interphase (90% of cycle) G1 phase~ growth S phase~ synthesis of DNA G2 phase~ preparation for cell division • Mitotic phase (10% of cycle) o Mitosis~ nuclear division o Cytokinesis~ cytoplasm division Bayan Al-Ghadeer Dalal Al-Anazi
    27. 27. Cell cycle control system
    28. 28. Cell cycle control system Involves •Cell cycle checkpoints •Specialized protein complex Function control the order and timing of the cell cycle. Bayan Al-Ghadeer Dalal Al-Anazi
    29. 29. Checkpoints ( control points ) They are pathways that: •Ensure that events are completed correctly before letting the cell enter the next phase. The checkpoint receive signals from : inside and outside the cell Bayan Al-Ghadeer Dalal Al-Anazi
    30. 30. Checkpoints There are 3 major checkpoints : I.at the end of G1 it is large & strong enough to continue with the cell division process II.at the end of G2 III. during mitosis phase it ensures if the spindles attached to the kinetochore within each chromosome Bayan Al-Ghadeer Dalal Al-Anazi
    31. 31. Specialized protein complex Is a combination of a Cycline & Cdk* to preform its work ( help the cell to enter the next phase) it has to be activated by phosphorylated at one site and dephosphorylated at the other site. kinase Bayan Al-Ghadeer * Cycline dependent Dalal Al-Anazi
    32. 32. Now we’ll see how much you’ve learned so raise your hand and wait your turn... Bayan Al-Ghadeer Dalal Al-Anazi
    33. 33. Cell Cycle interphase M I T O S I S Chromosomes appear, nucleus disappears prophase Chromatids pulled to poles metaphase Chromosomes invisible; DNA replicates anaphase Cytoplasmic division telophase Chromosomes at equator, spindle forms cytokinesis Bayan Al-Ghadeer Chromatids at poles, nucleus reforms Dalal Al-Anazi
    34. 34. Cell Increase and Decrease • Cell division: o Mitosis o Cytokinesis • Apoptosis (cell death) decreases the number of cells. • Both cell increase and apoptosis occur during normal development and growth. Bayan Al-Ghadeer Dalal Al-Anazi
    35. 35. Abnormal Division
    36. 36. Abnormalities • If there is a damage in DNA during G1 and the P53 is not present, the cell can’t stop entering into the next phase so, it will complete the cycle in an abnormal way.Then the cycle will be uncontrolled . • If a cell has extra protein BCL2 then it can absorb all of the death signals so the cell will prevent death(apoptosis) .That will leads to a high rate of mutation and the production of cells that tend to become cancerous ( tumor ) . Bayan Al-Ghadeer Dalal Al-Anazi
    37. 37. • The uncontrolled growth of cells in human to the disease called cancer. http://www.youtube.com/watch?v=vKIRWY-LMYc
    38. 38. • The uncontrolled growth of cells in human to the disease called cancer. http://www.youtube.com/watch?v=vKIRWY-LMYc
    39. 39. DNA
    40. 40. DNA & Mitosis • Before: – Chromosome duplicates = 2 sister chromatids (DNA replication ) • During: – Sister chromatids separate • After: – 2 “daughter” cells – Genetically identical Bayan Al-Ghadeer Dalal Al-Anazi
    41. 41. DNA structure • Two strands coiled called a double helix. • Center made of nitrogen bases bonded together by weak hydrogen bonds. • Stands for deoxyribonucleic acid made up of subunits called nucleotides. Bayan Al-Ghadeer Dalal Al-Anazi
    42. 42. constituents of nucleotide Bayan Al-Ghadeer Dalal Al-Anazi
    43. 43. Nucleotide made of: • Phosphate group • 5-carbon sugar • Nitrogenous base Bayan Al-Ghadeer Dalal Al-Anazi
    44. 44. Anti-parallel Strands •One strand of DNA goes from 5’ to 3’ •The other strand is opposite in direction going 3’ to 5’ Bayan Al-Ghadeer Dalal Al-Anazi
    45. 45. DNA Replication
    46. 46. Models of DNA replicate?“Possibilities” In this model , one daughter molecule contains both parental DNA strands, and the other daughter molecule contains DNA strands of all newly-synthesized material. Bayan Al-Ghadeer In this model two DNA double helices, both of which consist of one parental and one new strand. In this model the parental double helix is broken into doublestranded DNA segments .The segments assemble into complete DNA double helices from new and parental strands Dalal Al-Anazi
    47. 47. Steps of DNA replication 1. The DNA strands are separated at a specific area called origin . 2. The complementary strands are synthesized by DNA polymerase . 3. Termination : DNA polymerase goes throughout each strand in order to find errors and correct them. Bayan Al-Ghadeer Dalal Al-Anazi
    48. 48. Base pairing During Replication
    49. 49. Enzymes Required for Replication • Helicase: an enzyme that catalyzes the energy-dependent unwinding of the DNA double helix during DNA replication. • DNA polymerase: an enzyme that catalyzes the assembly of deoxyribonucleoside triphosphates into deoxyribonucleic acid, with single-stranded DNA serving as the template. The enzyme is often found in tumor cells. • Ligase : Joins together small newly synthesized pieces of DNA called Okazaki fragments. • Primase : Adds an RNA primer so that DNA synthesis can begin Bayan Al-Ghadeer Dalal Al-Anazi
    50. 50. Bayan Al-Ghadeer Dalal Al-Anazi
    51. 51. Summary  Abnormal division • What happens when DNA is damaged?  DNA Structure • constituents of nucleotides.  DNA Replication • Models of DNA replication. • Steps • Enzymes Required for Replication. Bayan Al-Ghadeer Dalal Al-Anazi
    52. 52. References • Essential cell biology – third edition • http://www.biologie.uni-hamburg.de/b-online/library/fal • http://www.phschool.com/science/biology_place/biocoa