Human Gametogenesis

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Human Gametogenesis
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Spermatogenesis

• Is the production of sperm in testes.
• When males reach sexual maturity (puberty),
  diploid spermatocytes undergo meiosis to produce
  haploid sperm.
• Each sperm possesses a flagellum, which enables
  it to move.
• Males can produce 1 billion sperm/day!
• Some spermatocytes continue to undergo mitosis to
  create a constant supply of cells with which to
  produce sperm.

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Spermatogenesis
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Oogenesis

• Is the production of eggs in the ovaries.
• At birth, a female will have all of the oocytes
  she will ever have.
• When females reach sexual maturity (puberty),
  each month a diploid oocyte undergo meiosis to
  produce one egg.

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Oogenesis, contd

• The end products of oogenesis are
• one large, haploid ootid which becomes the mature
  ovum (egg)
• three small, haploid polar bodies which
  disintegrate and die
• Cytokinesis is unequal - the ootid gets most of
  the cytoplasm and organelles to ensure the
  survival of the offspring should the egg be
  fertilized.

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Oogenesis
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Oogenesis, contd

• As a female ages, the number of oocytes declines
  until age 50-60.
• Menopause occurs when there are no more oocytes
  in the ovaries.

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Diverse Gametes

• How the chromosomes line up at the middle of the
  cell during Metaphase I and II is completely
  random.
• The formula to calculate the number of
  combinations is 2n
• For humans, n is 23. So 223 is
• over 8 million different combinations of
  chromosomes in gametes!!