BIOLOGY 171

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BIOLOGY 171 CHAPTER 13
MEIOSIS AND THE SEXUAL LIFE CYCLE
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OVERVIEW

• Asexual Reproduction
• Sexual Reproduction
• Somatic Cells
• Gametes
• Fertilization

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THE HUMAN LIFE CYCLE

• Homologous Chromosomes
• Sex Chromosomes
• Autosomes
• Haploid
• Diploid

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HUMAN LIFE CYCLE
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MEIOSIS AND THE SEXUAL LIFE CYCLE

• Meiosis - Reduction Division, Genetic
• Variation
• The Sexual Life Cycle
• Animals - Dominant Diploid Stage
• Fungi and Some Algae - Dominant
• Hapliod Stage
• Plants - Both Multicellular Haploid
• and Diploid Stages
• Look at Figure 12.4, Page 228.

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LIFE CYCLES
Fungus Algae
Animal Life Cycle
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PLANT LIFE CYCLE
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MEIOSIS VS. MITOSIS

• Two divisions but only one duplication of
• chromosomes
• Prophase I
• Pairing of homologous chromosomes
• Crossing-over, synapsis and chiasmata
• Metaphase I
• Paired homologues (tetrads) move to metaphase
  plate
• Anaphase I
• Diads move to opposite poles, not individual
  chromosomes

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MEIOSIS VS. MITOSIS

• Telophase I
• Daughter cells are haploid , but each
  chromosome is a diad.
• Interkinesis vs. Interphase
• No duplication of DNA in interkinesis
• Second Division and Telophase II
• The events of the second division are identical
  to the mitotic phases of mitosis except that
  the cells are haploid.
• Daughter cells in Telophase II are haploid if
  the original mother cell was diploid.

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MEIOSIS VS. MITOSIS
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MEIOSIS
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MEIOSIS
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MEIOSIS
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MEIOSIS
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INCREASED GENETIC VARIATION

• Crossing Over
• Synapsis
• Chiasmata
• Independent Assortment of Homologous
  Chromosomes
• Random Fertilization

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INDEPENDENT ASSORTMENT
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CROSSING OVER
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SPERMATOGENESIS
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OOGENESIS