Chapter 7 The cell cycle.ppt
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- 2. 6/1/2023 Mr. Harun Ismail Warsame 2 AMOUD UNIVERSITY SCHOOL OF DENTISTRY 1ST YEAR STUDENTS Course Title: DNS 6111 Course Code: Cytology Lecturer: Harun Ismail Warsame(BSc/MPH)
- 3. Learning Objectives 1. Define cell division. 2. Explain the cell cycle. 3. Distinguish between mitosis and meiosis. 4. Describe the stages of mitosis. 6/1/2023 Mr. Harun Ismail Warsame 3 Chapter 7: The cell division and Cell Cycle
- 4. Cell division 6/1/2023 Mr. Harun Ismail Warsame 4 20 µm Cell division: is the process by which one cell produces two or more daughter cells. 200 µm (a) An amoeba, a single-celled eukaryote, is dividing into two cell (b) Growth and development. This embryo shortly after the fertilized egg divided, forming two cells (c) Tissue renewal. These dividing bone marrow cells will give rise to new blood cells
- 5. Cell Cycle The cell cycle is a repeated pattern of growth and division that occurs in eukaryotic cells. 6/1/2023 Mr. Harun Ismail Warsame 5
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- 7. Phases of cell cycle 6/1/2023 Mr. Harun Ismail Warsame 7 Cell cycle consist of two phase interphase phase mitosis phase
- 8. Interphase 6/1/2023 Mr. Harun Ismail Warsame 8 G1 - Cells undergo majority of growth S - Each chromosome replicates (Synthesizes) G2 - Chromosomes condense - Assemble machinery for division such as centrioles
- 9. 6/1/2023 Mr. Harun Ismail Warsame 9 Almost 90% of the cycle is taken up with Interphase during which DNA in the nucleus is replicated Mitosis and cytokinesis only take up 10% of cycle
- 10. The cell cycle has four main stages. 6/1/2023 Mr. Harun Ismail Warsame 10 The cell cycle is a regular pattern of growth, DNA replication, and cell division.
- 11. 6/1/2023 Mr. Harun Ismail Warsame 11 The main stages of the cell cycle are gap 1, synthesis, gap 2, and mitosis. – Gap 1 (G1): cell growth and normal functions • Mitosis occurs only if the cell is large enough and the DNA undamaged. – DNA synthesis (S): copies DNA – Gap 2 (G2): additional growth (chromatids become replicated chromosomes) – Mitosis (M): includes division of the cell nucleus (mitosis) and division of the cell cytoplasm (cytokinesis)
- 12. Mitosis 6/1/2023 Mr. Harun Ismail Warsame 12 haploid and diploid cells divide by mitosis. Each new cell receives one copy of every chromosome that was present in the original cell. Produces 2 new cells that are both genetically identical to the original cell.
- 13. Condensed, duplicated chromosome 6/1/2023 Mr. Harun Ismail Warsame 13
- 14. 6/1/2023 Mr. Harun Ismail Warsame 14 DNA plus proteins is called chromatin. • One half of a duplicated chromosome is a chromatid. • Sister chromatids are held together at the centromere. • Telomeres protect DNA and do not include genes. Condensed, duplicated chromosome chromatid telomere centromere telomere
- 15. Mitosis •The purpose of mitosis is cell division: making two cells out of one. • Each cell has to have its own cytoplasm and DNA. •The DNA is replicated in interphase when two chromosome strands became four strands (two strands per chromatid). •In mitosis the four strands (two sister chromatid) have to break apart so that each new cell only has one double-stranded chromosome. •Two sister chromatids together make a chromosome 6/1/2023 Mr. Harun Ismail Warsame 15
- 16. Mitosis 6/1/2023 Mr. Harun Ismail Warsame 16 Interphase Prophase I P M A T Metaphase Anaphase Telophase
- 17. Interphase 6/1/2023 Mr. Harun Ismail Warsame 17 1. Cell preparing to divide 2. Genetic material doubles
- 18. Prophase 6/1/2023 Mr. Harun Ismail Warsame 18 1. Chromosomes thicken and shorten -become visible -2 chromatids joined by a centromere 2. Centrioles move to the opposite sides of the nucleus 3. Nucleolus disappears 4. Nuclear membrane disintegrate
- 19. Metaphase 6/1/2023 Mr. Harun Ismail Warsame 19 Chromosomes meet in the middle! 1. Chromosomes arrange at equator of cell 2. Become attached to spindle fibres by centromeres
- 20. Anaphase 6/1/2023 Mr. Harun Ismail Warsame 20 Chromosomes get pulled apart 1. Spindle fibres contract pulling chromatids to the opposite poles of the cell
- 21. Telophase 6/1/2023 Mr. Harun Ismail Warsame 21 Now there are two! 1. Chromosomes uncoil 2. Spindle fibres disintegrate 3. Centrioles replicate 4. Nucleur membrane forms 5. Cell divides
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- 25. Cells divide at different rates. 6/1/2023 Mr. Harun Ismail Warsame 25 The rate of cell division varies with the need for those types of cells.
- 26. Class Activity Do the following Questions 1. During what phase of mitosis do centromeres divide and the chromosomes move toward their respective poles? 2. What is the phase where chromatin condenses to form chromosomes? 6/1/2023 Mr. Harun Ismail Warsame 26
- 27. 3. What is the name of the structure that connects the two chromatids? 6/1/2023 Mr. Harun Ismail Warsame 27
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