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1.6 Cell Division/Mitosis

Explore the intricate process of cell division through mitosis stages, the cell cycle, and its significance in growth, repair, and reproduction. Learn about the control mechanisms, mutagens, tumors, and metastasis.

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1.6 Cell Division/Mitosis

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  1. 1.6 Cell Division/Mitosis

  2. Question? • Why would a cell want or need to divide? • Growth/development of tissues/organs • Repair of damaged tissue/organ • Reproduction of cells/organisms

  3. Cell Cycle • The cell’s life cycle (usually just called the cell cycle) consists of two main parts: • Interphase – active period in the life of a cell when many metabolic reactions occur, including • protein synthesis • DNA replication • an increase in the number of mitochondria and/or chloroplasts • Mitosis– cell divides

  4. Cell Cycle • Interphase can be divided into three phases: • G1 – cell grows and metabolizes • S – DNA is replicated • G2 – cell prepares for division

  5. Mitosis • Mitosis can be divided into four stages: • Prophase • Metaphase • Anaphase • Telophase

  6. Mitosis • Prophase • Nuclear envelope disappears • With the aid of special proteins called histones, DNA supercoils into distinct chromosomes that are visible under the microscope • Each pair of identical segments of DNA, called sister chromatids, bind together at the centromere to form one chromosome

  7. Prophase • Centrioles moved to opposite ends of the cell • Long, tubular proteins called “spindle fibers” grow from the centrioles and attach to the centromeres of the chromosomes

  8. Metaphase • Spindle fibers pull chromosomes to the equator (center line) of the cell

  9. Anaphase • Spindle fibers shorten • Sister chromatids are pulled apart and are now called chromosomes • Chromosomes are pulled to opposite ends of the cell

  10. Telophase • Reverse of prophase: • Spindle fibers dissapear • DNA uncoils and becomes chromatin • Nuclear envelope reforms

  11. Cytokinesis • Splitting of the cytoplasm • Occurs when microtubule proteins pinch inward at the equator (cleavage furrow) • Results in two separate but identical cells

  12. Plant Cell Division • In plants a cell plate forms instead of a cleavage furrow

  13. Overview • Mitosis produces two genetically identical nuclei • During the S phase of interphase DNA is replicated to produce two identical copies • During prophase the identical copies of each chromosome (homologous chromsomes) bind together • Homologous chromosomes are pulled apart during anaphase and become part of two separate nuclei during telophase

  14. Mitosis serves many purposes: • Tissue/organ growth • Embryonic devleopment, when the zygote divides to produce many smaller cells • Tissue damage and repair • Asexual reproduction (unicellular organisms)

  15. Control of this process • Cyclins • Series of proteins that control cells during cell cycle.

  16. Not always controlled • Mutagens – • Physical or chemical agent that changes the DNA in an organism. • This increases the frequency of mutations in that organism above the natural background level. • Often these mutagens can cause cancer/tumors

  17. Oncogenes • Sometimes the gene controlling cell division (called an oncogene) will become mutated • The result is that cell division continues repeatedly • This is how tumors are formed • Tumors can form in any tissue of the body Stomach Tumor

  18. Metastasis • Greek for “Next Placement” • Cells that are going through uncontrolled proliferation can sometimes slough off of a tumor and spread through the body to another area that previously was unaffected. • These cells will continue their rapid mitotic division and cause the disease to spread.

  19. Tumors • Tumors are a mass of cells that are going through mitosis uncontrollably due to a mutation in the DNA • Two major types: • Malignant: “Badly Born” can spread to invade other cells throughout the body. • Benign: lacks the ability to invade neighboring cells

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