Meiosis

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Meiosis
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Meiosis Meiosis Meiosis Meiosis

• Defined Process where the chromosome number is
  reduced by half
• Gametes created (egg sperm)
• End Result Four Haploid Cells

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Interphase

• Same process (G1, S, G2)
• Chromatin duplicated

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Synthesis (S stage)
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Prophase 1

• Similar as mitosis, except
• Two Events
• 1) Synapsis Pairing of homologous chromosomes
• The four chromatids equal a TETRAD
• 2) Crossing Over Exchange of genes

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Early Prophase
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Synapsis Homologous chromosomes align
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Metaphase 1

• Homologous chromosomes (tetrads) align along cell
  equator

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Anaphase 1

• Homologous chromosomes are pulled apart to
  opposite ends
• Tetrads separated

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Telophase 1

• Cytokinesis divides the cells
• Each cell contains 1 of the homologous
  chromosomes (23 total)

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Prophase 2

• Same as mitosis
• Note No new DNA was created (no 2nd interphase)

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Metaphase 2

• Remaining chromosomes are aligned at cell equator

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Anaphase 2

• Sister chromatids are pulled to opposite ends

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Telophase 2

• Nucleus reforms on the four new cells
• Cytokinesis divides the cells
• Chromatids uncoil
• End Result Four haploid cells

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Spermato- genesis

• Defined Production of sperm cells
• Occurs in male testes
• Meiosis produces four haploid sperm cells at a
  time

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• Defined Production of the egg cell (ovum)
• During meiosis I Cytoplasm distributed unequally
• After meiosis II
• 1 cell matures
• 3 Polar Bodies dissolve

Oogenesis
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Meiosis
Mitosis

• Division resulting in gametes
• Ex Sperm and Egg cells
• End Result 4 Haploid cells
• Importance Reduces the gamete chromosome number
  by half

• Division of somatic cells
• Ex Blood cells, skin cells, nerve cells
• End Result 2 Diploid Cells
• Importance Replaces aging cells
• Importance Form of asexual reproduction