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Cell Division

Learn about the process of cell division through mitosis and meiosis, the structure and function of chromosomes, and the different stages of the cell cycle. Understand how the cell cycle is regulated and the implications of uncontrolled cell growth, such as cancer.

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Cell Division

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  1. Cell Division Mitosis and Meiosis

  2. Chromosomes • Chromatin – long strands of DNA wrapped around proteins • Chromosome – a rod-shaped structure that forms when a single DNA molecule coils tightly before cell division

  3. Single Chromosome Duplicated Chromosome

  4. Chromatid– one of two copies of each chromosome • Sister Chromatid – two identical copies of the chromatid • Centromere – a protein disk that attaches the two chromatids

  5. Single Chromosome Duplicated Chromosome Centromere Chromatid Chromatid Sister Chromatids

  6. Human cells have 23 different chromosomes • Contain 2 copies of each chromsome for a total of 46 • Homologous chromosomes – two copies of each chromosome that are similar in shape, size and have similar genetic information

  7. Cell Division • Cell division – process by which new cells are made from an existing cell • Two types of cell division • Mitosis – makes somatic cells (body cells) • Meiosis – makes gametes (sperm and egg)

  8. The Cell Cycle • Cell Cycle – sequence of growth and division of a cell • 5 Phase of the Cell Cycle • G1 • Growth of cell • Makes new proteins and organelles

  9. 2. S • DNA replicates • 3. G2 • Produces proteins needed for mitosis or meiosis • 4. M • Mitosis or Meiosis • Cytokinesis – cytoplasm divides separating into 2 daughter cells • G1, S, and G2 combined are called Interphase • Where the cell spends most of its life

  10. Interphase G1 S Cytokinesis C Telophase Anaphase Metaphase G2 Prophase Mitosis Video

  11. Mitosis • Mitosis – process by which the nucleus of a cell is divided into 2 identical nuclei with the same number of chromosomes • Mitosis is divided into 4 stages

  12. 1. Prophase • Chromatin coils into chromosomes • Nuclear envelope breaks down • Centrioles form and move to opposite poles • As centrioles separate, spindle fibers form which are microtubules (protein cables) • Longest phase of mitosis

  13. 2. Metaphase • Spindle fibers attach to the chromosomes at the centromere • Chromosomes line up in the middle

  14. 3. Anaphase • Centromeres split and sister chromatidsare pulled apart toward opposite poles • Each chromatid may now be called a single chromosome

  15. 4. Telophase • Chromosomes reach opposite poles • Spindle fibers break • Chromsomes uncoil • Nuclear envelope forms

  16. Cytokinesis • Two daughter cells are formed Video

  17. Cytokinesis differs between plants and animals • Animals – the cell membrane pinches in along the center of the cell

  18. Plants – have a cell wall so cell membrane can’t pinch in • Instead a cell plate is laid down across the center

  19. The Cell Cycle

  20. Regulating the Cell Cycle • Normal Cell Growth • Scientists have worked long and hard to discover the factors that initiate and control cell division. • A clear understanding of these control factors can benefit medical research. • Scientists have found that a specific protein called cyclin regulates the cell cycle.

  21. Uncontrolled Cell Growth • Occasionally cells lose control of the cell cycle • This loss of control may be caused by… • Environmental factors • Changes in enzyme production • Cancer is a result of uncontrolled cell division • Cancer cells divide uncontrollably and form masses of cells called tumors. • Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death.

  22. Cancer

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