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Chapter 8.3

Chapter 8.3. Meiosis. Types of Reproduction. Asexual reproduction Produce offspring with only ONE parent “babies” are identical to parent Sexual reproduction Produce offspring by meiosis and the joining of the sperm and egg “babies” are NOT identical to parents. Meiosis

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Chapter 8.3

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  1. Chapter 8.3 Meiosis

  2. Types of Reproduction • Asexual reproduction • Produce offspring with only ONE parent • “babies” are identical to parent • Sexual reproduction • Produce offspring by meiosis and the joining of the sperm and egg • “babies” are NOT identical to parents

  3. Meiosis • New cells have half the number of chromosomes • Gametes • Reproductive cells (sperm and egg)

  4. Key Points • Meiosis must happen so when the sperm and egg join to create a new organism, it has the correct number of chromosomes. • Examples: • Human = 46 • Egg = 23 • Sperm = 23 • Egg + Sperm = baby • 23 + 23 = 46

  5. Meiosis I. (very similar to mitosis) • Prophase I. • DNA coils into chromosomes • Each chromosome lines up with its homologue (the similar chromosomes) • Synapsis: pairing of homologous chromosomes • Each pair is called a tetrad • Crossing-over: may occur where pieces of one chromosome break off and attach to the other chromosome  genetic recombination

  6. Metaphase I. • Tetrads line up along the middle of the cell

  7. Anaphase I. • Each homologous chromosome of each tetrad moves to opposite ends of the cell

  8. Telophase I. • Cell divides creating 2 new cells each with a haploid number of chromosomes (1/2 the original number of chromosomes, but 2 copies of each)

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