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Understanding Mitosis and Meiosis Processes

Mar 3, 2025

Mitosis and Meiosis Lecture Notes

Overview

  • Mitosis: Cellular division resulting in two identical daughter cells.
  • Meiosis: Cellular division resulting in four genetically diverse cells with half the original chromosome number.

Mitosis

Key Concepts

  • Simple duplication of a cell and all its parts.
  • Produces two identical daughter cells with identical genetic material.

Phases

Interphase

  • Preparation phase involving protein synthesis, DNA duplication.

Karyokinesis

  1. Prophase

    • Chromosomes condense and become visible.
    • Nuclear envelope disintegrates.
    • Spindle apparatus forms.

  2. Metaphase

    • Chromosomes align along the central axis.
    • Spindle fibers attach to centromeres.

  3. Anaphase

    • Chromosomes are pulled apart to opposite sides of the cell.

  4. Telophase

    • Nuclear envelopes re-form around chromosomes.
    • Cytokinesis occurs, splitting the cell into two.

Significance

  • Enables growth and development of multicellular organisms.
  • Maintains chromosome numbers in daughter cells.
  • Aids in tissue repair and regeneration.
  • Unchecked mitosis can lead to cancer.

Meiosis

Key Concepts

  • Division producing four haploid cells (sex cells).
  • Adds genetic diversity through recombination.

Phases

Interphase

  • DNA replication results in two sets of chromosomes.

Meiosis I

  1. Prophase I

    • Homologous chromosomes pair and exchange DNA (crossing over).
    • Formation of bivalents or tetrads.

  2. Metaphase I

    • Homologous pairs align along the metaphase plate.

  3. Anaphase I

    • Homologous chromosomes pulled to opposite poles.

  4. Telophase I and Cytokinesis

    • Chromosomes arrive at poles, cell divides into two haploid cells.

Meiosis II

  • Similar process to mitosis, separates sister chromatids.

  1. Prophase II

    • Chromatids condense, nuclear envelope disintegrates.

  2. Metaphase II

    • Chromatids align at the equatorial plane.

  3. Anaphase II

    • Sister chromatids separate.

  4. Telophase II and Cytokinesis

    • Resulting in four genetically distinct haploid cells.

Significance

  • Generates genetic diversity among offspring.
  • Essential for sexual reproduction.

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