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Somatic Cell Division

This article delves into somatic cell division through mitosis, a vital process that occurs in all body cells except gametes. It outlines the intricate DNA replication steps necessary for cell division, highlighting the cell cycle's two main phases: Interphase and Mitotic Phase. During Interphase, the cell replicates its DNA and prepares for division, while the Mitotic Phase includes the complex process of nuclear division through prophase, metaphase, anaphase, and telophase. The role of cytoplasmic division (cytokinesis) is also explored, culminating in the formation of two identical daughter cells.

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Somatic Cell Division

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  1. Somatic Cell Division Mitosis

  2. Somatic Cells • All body cells except gametes (sex cells)

  3. Somatic Cell Division • A cell divides into two identical cells • Replaces dead or injured cells • Adds new cells for tissue growth

  4. DNA Replication (Duplication) • The DNA sequences that make up the chromosomes have to be copied so the same genetic material can be passed on to the new cells

  5. Cell Cycle • The sequence of changes a cell undergoes from the time it forms until the time it duplicates its contents and divides into 2 cells • Two major time periods: • Interphase – not dividing • Mitotic Phase - dividing

  6. Interphase • The cell replicates DNA and manufactures additional cell organelles and cytosolic components • High metabolic activity • Most growth

  7. DNA Replication • DNA nucleotides are synthesized in the cytosol and imported to the nucleus • The helical DNA uncoils and the 2 strands separate between the base pairs • The exposed base pair on each strand pairs with a newly synthesized complementary nucleotide • The new DNA strands take shape as chemical bonds form

  8. DNA Replication - continued • The original DNA molecule has become 2 identical strands of DNA • Once a cell completes DNA replication, the mitotic phase can begin.

  9. Mitotic Phase • Mitosis – division of the nucleus • Cytokinesis – division of the cytoplasm

  10. Nuclear Division • The duplicated chromosomes become divided such that one set ends up in each nucleus • The process is divided into 4 stages: • Prophase, Metaphase, Anaphase and Telophase **Mitosis is a continuous process and one phase merges with the next**

  11. Prophase • Chromatin fibers condense and shorten into chromosomes • Each prophase chromosome consists of a pair of identical double stranded chromatids • Mitotic Spindle is formed by the pericentriolar material and centrioles are pushed to opposite sides of the cell • The nucleolus and nuclear envelope break down

  12. Metaphase • The centromeres of the chromatid pairs are aligned along the center of the mitotic spindle – this is called the metaphase plate

  13. Anaphase • The centromeres split, separating the chromatid pair, which move to opposite ends of the cell. • Once separated the chromatids are called chomosomes.

  14. Telophase • Final stage of mitosis • Begins when chromosome movement stops • The chromosomes start to uncoil, a new nuclear envelope forms, nucleoli appear and the mitotic spindle breaks up. • TWO nuclei are present and the cell starts to divide into 2

  15. Cytoplasmic Division - cytokinesis • Division of the cell’s cytosol and organelles • Begins in late anaphase/early telophase with the formation of a cleavage furrow • Cleavage Furrow – slight indentation of the plasma membrane

  16. Checkpoint • What is the difference between a chromatid and a chromosome? • In which stage of the cell cycle is the cell growing? • What are the mitotic phases in order? • What is a major event in each stage?

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