Meiosis: Making reproductive cells

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Meiosis Making reproductive cells

• Meiosis the process of nuclear division where
  the number of the chromosomes is halved.
• produces four daughter cells
• all daughter cells are haploid (n)
• chromosomes are shuffled in the process, so that
  each daughter cell has a unique combination (it
  produces many different reproductive cells.)
• process that makes gametes (sperm and egg)

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Crossing-Over

• Chromosomes exchange sections - Crossing over
  increases variability/diversity
• Crossing-over increases the already huge number
  of different gamete types produced by independent
  assortment

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Spermatogenesis Production of male gametes
(sperm)Oogenesis Production of female gametes
(eggs)
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Spermatogenesis

• Occurs in the testes
• Two divisions produce 4 sperm cells
• Men produce about 250,000,000 sperm per day

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Oogenesis

• Occurs in the ovaries
• Two divisions produce 3 polar bodies that die and
  1 egg
• Polar bodies die because of unequal division of
  cytoplasm
• Starting at puberty,
• one egg matures
• every 28 days

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Comparing Mitosis and Meiosis
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Mitosis vs. Meiosis

• Mitosis
• Cell division of body cells (somatic)
• Produces 2 diploid cells (2n)
• Each new cell contains copies of all chromosomes
• One cell division
• All cells are identical (photocopies)

• Meiosis
• Cell division that produces gametes
• Produces 4 haploid cells (n)
• Each gamete contains just one chromosome of each
  pair
• Two cell divisions
• All cells are different (diversity)

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Fertilization