Stages of Meiosis Summary Notes

Stages of Meiosis Simple Notes

Definition of Meiosis: A type of cell division that produces four haploid cells with half the number of chromosomes from a diploid parent cell.

You can watch our 4 minute video here Stages of Meiosis

You can watch our 3 minute video here Stages of mitosis

Functions of Meiosis

  • Essential for sexual reproduction: Meiosis reduces the chromosome number by half, creating four haploid cells from one diploid cell, essential for sexual reproduction.
  • Formation of Gametes: Meiosis produces gametes (sperm and eggs in animals, pollen and ovules in plants) that are necessary for fertilization.
  • Genetic Variation: Meiosis generates genetic variation through crossing over and independent assortment which is crucial for evolution and adaptation.

Meiosis is divided into 2 major stages Meiosis I and Meiosis II

  • In Meiosis I: A parent diploid cell forms 2 haploid cells
  • In Meiosis II: 2 haploid cell forms 4 haploid cells; just like mitosis
Stages of Meiosis Summary Notes

Meiosis I is divided into 4 substages; Prophase I, Metaphase I, Anaphase I and Telophase I

Prophase I

Chromosomes condenses and become visible

  • Homologous chromosomes* pair up (synapsis), forming tetrads (homologous chromosome pair has 4 chromatids; so, called tetrads.)
  • Crossing over occurs; it is the exchange of segments between homologous chromosomes that lead to genetic variation.
  • Nuclear envelope breaks down and spindle fibers form
*Homologous chromosomes are chromosomes with similar length, gene position and centromeric position; one inherited from father and one from mother

Metaphase I

  • The nucleus disappears.
  • Tetrads or homologous chromosomes align at the metaphase plate or at the center
  • Spindle fibers attach to the centromeres of homologous chromosomes

Anaphase I

  • The homologous chromosomes are pulled apart at the centromere and move toward opposite poles of the cell.
  • Spindle fibres begin to shorten.
  • This separation ensures that each new daughter cell will receive half the set of chromosomes of the parent cell

Telophase I

  • Chromosomes arrive at opposite poles and begin to decondense back into chromatin
  • Nuclear envelopes begin to reform around each set of chromosomes
  • The spindle fibres break down.
  • During cytokinesis, the cytoplasm divides, resulting in two separate daughter cells, with chromosome number reduced to half.

Why is Meiosis I called as reduction division?

From a diploid parent cell; 2 haploid cells are formed (chromosome number reduced to half) in Meiosis I; so, called as reduction division

Meiosis II is divided into 4 substages; Prophase II, Metaphase II, Anaphase II and Telophase II

Stages of Meiosis Summary Notes

Prophase II

  • Chromosomes condenses and become visible again in each haploid cell
  • Nuclear envelope breaks down and spindle fibers form

Metaphase II

  • The nucleus disappears.
  • Chromosomes align at the metaphase plate or at the center
  • Spindle fibers attach to the centromeres of the chromosomes

 Anaphase II

  • The sister chromatids are pulled apart at the centromere and move toward opposite poles of the cell.
  • Spindle fibres begin to shorten.

Telophase II

  • Chromatids arrive at opposite poles and begin to decondense back into chromatin
  • Nuclear envelopes begin to reform around each set of chromosomes
  • The spindle fibres break down.
  • During cytokinesis, the cytoplasm divides, resulting in four genetically unique haploid cells

Why is Meiosis II called as equational division?

From 2 parent haploid cell; 4 haploid cells are formed with same chromosome number just like mitosis; so, called as equational division.

Suggest Content: Stages of Mitosis Simple Summary notes

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