Mitosis vs Meiosis

Introduction

• Mitosis and meiosis are mechanisms of cell division in eukaryotes.
• They are crucial for growth, development, and genetic diversity but differ in function and outcomes.
  • Mitosis: Produces two diploid daughter cells (growth and repair).
  • Meiosis: Produces four haploid daughter cells (making sex cells).

Definitions

Mitosis

• Produces two genetically identical daughter cells.
• Functions in:
  • Growth
  • Tissue repair
  • Asexual reproduction in some organisms
• Part of the cell cycle.

Meiosis

• Produces gametes (sperm, egg, spores).
• Results in four non-identical daughter cells with half the chromosome number.
• Important for:
  • Sexual reproduction
  • Genetic diversity

Steps of Mitosis and Meiosis

Mitosis Steps

1. Interphase: DNA replication.
2. Prophase: Chromosomes condense; nuclear envelope dissolves.
3. Metaphase: Chromosomes align at the equatorial plane.
4. Anaphase: Sister chromatids separate.
5. Telophase: New nuclear envelopes form.
6. Cytokinesis: Cytoplasm divides, forming two identical cells.

Meiosis Steps

• Meiosis I
  1. Interphase: DNA replication.
  2. Prophase I: Homologous pairing; crossing-over occurs.
  3. Metaphase I: Homologous pairs align.
  4. Anaphase I: Homologous chromosomes separate.
  5. Telophase I: Nuclear membranes reform; cytokinesis.
• Meiosis II
  1. Prophase II: Chromosomes condense; nuclear envelope dissolves.
  2. Metaphase II: Chromosomes align.
  3. Anaphase II: Sister chromatids separate.
  4. Telophase II: Nuclear membranes reform; cytokinesis, resulting in four non-identical daughter cells.

Similarities

• Both start with a single parent cell.
• Both have an interphase stage where DNA replication occurs.
• Share fundamental stages: prophase, metaphase, anaphase, telophase.

Differences

Cell Division Cycles

• Mitosis: One cycle
• Meiosis: Two cycles

Outcomes and Functions

• Mitosis: Two identical diploid daughter cells
• Meiosis: Four non-identical haploid daughter cells

Specific Stage Differences

• Interphase
  • Mitosis: Creates identical sister chromatids.
  • Meiosis: Crossing-over introduces genetic diversity.
• Prophase
  • Mitosis: No homologous pairing/crossing-over.
  • Meiosis: Homologous pairing and crossing-over occur.
• Metaphase
  • Mitosis: Individual chromosomes align.
  • Meiosis: Homologous pairs align in Metaphase I.
• Anaphase
  • Mitosis: Sister chromatids separate.
  • Meiosis: Anaphase I separates homologous chromosomes; Anaphase II separates sister chromatids.

Summary Table

References

• Maton, A.; Hopkins, J.J.; et al. (1997). Cells: Building Blocks of Life. New Jersey: Prentice Hall.
• Hassold, T.; Hunt, P. (2001). To err (meiotically) is human: the genesis of human aneuploidy.
• Hunter, N. (2015). Meiotic Recombination: The Essence of Heredity.
• Snustad, D.P.; Simmons, M.J. (2008). Principles of Genetics.