grate CELL DIVISION AND DNA REPLICATION.ppt
- 1. Cell Division Cell Division Mitosis- Cell reproduction Mitosis- Cell reproduction
- 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. Key Words • Chromosome • chromatin • centriole & centrosome • centromere & kinetochore • chromatid
- 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. chromatin Chromatin is the building block for a chromosome. It consists of DNA and proteins. Bayan Al-Ghadeer Dalal Al-Anazi
- 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. 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. 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. Sister chromatids Bayan Al-Ghadeer Dalal Al-Anazi
- 9. Ready? Let’s begin Bayan Al-Ghadeer Dalal Al-Anazi
- 10. Cell division Bayan Al-Ghadeer Dalal Al-Anazi
- 11. Why do cells divide? •Growth •Repair and replace dead cells •asexual reproduction Bayan Al-Ghadeer Dalal Al-Anazi
- 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. Interphase Estimated (90% of cycle) 3 phases •G1 phase •S phase •G2 phase Bayan Al-Ghadeer Dalal Al-Anazi
- 15. • Growth of cell. • Dupliction of organelles. • Synthisis of proteins. G1 phase Bayan Al-Ghadeer Dalal Al-Anazi
- 16. • DNA synthesis occurs • DNA replication results in duplicated chromosomes • centrosome cycle S phase Bayan Al-Ghadeer Dalal Al-Anazi
- 17. • 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 G2 phase Bayan Al-Ghadeer Dalal Al-Anazi
- 18. Estimated (10% of cycle) Includes 2 parts : 1)Mitosis •Prophase •Promataphase •Metaphase •Anaphase •Telophase 2) Cytokinesis M phase Bayan Al-Ghadeer Dalal Al-Anazi
- 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. 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. Duration (15 min) • The nuclear membrane disappears. • Kinetochores will get attached to the centromere. • The spindle fibers become attached to the kinetochore. Prometaphase Bayan Al-Ghadeer Dalal Al-Anazi
- 22. 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. Metaphase Bayan Al-Ghadeer Dalal Al-Anazi
- 23. 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. Anaphase: Bayan Al-Ghadeer Dalal Al-Anazi
- 24. 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. Telophase: Bayan Al-Ghadeer Dalal Al-Anazi
- 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
- 27. Summary • Interphase (90% of cycle) o G1 phase~ growth o S phase~ synthesis of DNA o 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
- 28. Cell cycle control system
- 29. 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
- 30. ( 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 Checkpoints Bayan Al-Ghadeer Dalal Al-Anazi
- 31. 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 Checkpoints Bayan Al-Ghadeer Dalal Al-Anazi
- 33. 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. * Cycline dependent kinase Specialized protein complex Bayan Al-Ghadeer Dalal Al-Anazi
- 34. Now we’ll see how much you’ve learned so raise your hand and wait your turn... Bayan Al-Ghadeer Dalal Al-Anazi
- 35. Cell Cycle M I T O S I S interphase prophase metaphase anaphase telophase cytokinesis Chromosomes invisible; DNA replicates Chromosomes appear, nucleus disappears Chromatids pulled to poles Cytoplasmic division Chromosomes at equator, spindle forms Chromatids at poles, nucleus reforms Bayan Al-Ghadeer Dalal Al-Anazi
- 36. 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
- 38. • 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 ) . Abnormalities Bayan Al-Ghadeer Dalal Al-Anazi
- 39. http://www.youtube.com/watch?v=vKIRWY-LMYc • The uncontrolled growth of cells in human to the disease called cancer.
- 40. http://www.youtube.com/watch?v=vKIRWY-LMYc • The uncontrolled growth of cells in human to the disease called cancer.
- 41. DNA
- 42. • Before: – Chromosome duplicates = 2 sister chromatids (DNA replication ) • During: – Sister chromatids separate • After: – 2 “daughter” cells – Genetically identical DNA & Mitosis Bayan Al-Ghadeer Dalal Al-Anazi
- 43. 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
- 44. constituents of nucleotide Bayan Al-Ghadeer Dalal Al-Anazi
- 45. • Phosphate group • 5-carbon sugar • Nitrogenous base Nucleotide made of: Bayan Al-Ghadeer Dalal Al-Anazi
- 46. 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
- 47. DNA Replication
- 48. 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. 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 double- stranded DNA segments .The segments assemble into complete DNA double helices from new and parental strands Bayan Al-Ghadeer Dalal Al-Anazi
- 49. 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. Steps of DNA replication Bayan Al-Ghadeer Dalal Al-Anazi
- 50. Base pairing During Replication
- 51. 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
- 52. Bayan Al-Ghadeer Dalal Al-Anazi
- 53. Abnormal division • What happens when DNA is damaged? DNA Structure • constituents of nucleotides. DNA Replication • Models of DNA replication. • Steps • Enzymes Required for Replication. Summary Bayan Al-Ghadeer Dalal Al-Anazi
- 55. • Essential cell biology – third edition • http://www.biologie.uni-hamburg.de/b-online/librar y/falk/cellDivision/division.htm • http://www.phschool.com/science/biology_place/bi ocoach/dnarep/classical.html References
Editor's Notes
- #12: 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