MEIOSIS

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MEIOSIS
Creating gametes (sex cells)
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Chromosome Number

• A human body cell has 46 chromosomes
• 23 from dad and 23 from mom
• These sets of chromosomes are homologous, meaning
  that each chromosome that came from dad has a
  corresponding chromosome from mom.

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Diploid and Haploid

• A cell that contains both sets of homologous
  chromosomes is said to be diploid.
• Diploid two sets, 2N, or 2N46
• A cell that only contains 1 set of chromosomes is
  said to be haploid.
• Haploid one set, N, or N23

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Phases of Meiosis

• Occurs in 2 divisions- meiosis I and meiosis II
• In the end one diploid cell will become 4 haploid
  cells

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Crossing Over occurs in Meiosis I

• 1. Homologous chromosomes form a tetrad
• 2. Chromatids cross over one another
• 3. The crossed sections of chromatids are
  exchanged
• 4. This produces a new combination of genes which
  contributes to diversity within a population.

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Gamete Formation occurs in Meiosis II

• Meiosis I results in 2 haploid daughter cells
• Meiosis II results in 4 haploid daughter cells
• The haploid gamete in males is sperm
• The haploid gamete in females is the egg

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Comparing Mitosis and Meiosis

• Mitosis
• Results in 2 identical diploid cells
• Involves asexual reproduction
• 1 division

• Meiosis
• Results in 4 genetically different haploid cells
• Involves sexual reproduction
• 2 divisions

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