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Chapter 11-4 Meiosis

Chapter 11-4 Meiosis. Meiosis Vocabulary. Diploid Haploid Gametes Homologous chromosomes Crossing over Tetrad. So lets talk about making a person. So who do you look like? What holds the genetic information? How is this genetic information passed to the next child?

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Chapter 11-4 Meiosis

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  1. Chapter 11-4 Meiosis

  2. Meiosis Vocabulary • Diploid • Haploid • Gametes • Homologous chromosomes • Crossing over • Tetrad

  3. So lets talk about making a person • So who do you look like? • What holds the genetic information? • How is this genetic information passed to the next child? • How many sets of chromosomes do you have? • What are homologous chromosomes? • Where do you get your sets of chromosomes?

  4. Meiosis • Most cells have two sets of chromosomes • This is called diploid (2 sets of 23) • 2n = diploid #, humans 2n = 46 • Gametes have one set of chromosomes • This is called haploid cell (1 set of 23) • n = haploid #, humans n = 23 • Sperm, egg, pollen are examples • Meiosis is the process of making haploid cells from diploid cells • Haploid + haploid = diploid /fertilization

  5. Meiosis • Meiosis has two divisions • meiosis 1 • meiosis 2 • Meiosis 1 • First division separates the homologous chromosomes • Crossing over of genetic material can take place • Meiosis 2 • 2nd division separates the sister chromatids into individual chromosomes • Process is like mitosis • Except for the number of chromosomes • Each division has same 4 ‘steps’ • Prophase, metaphase, anaphase, telophase

  6. Figure 11-15 Meiosis Section 11-4 Meiosis I Interphase I Prophase I Metaphase I Anaphase I Cells undergo a round of DNA replication, forming duplicate Chromosomes. Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. Spindle fibers attach to the chromosomes. The fibers pull the homologous chromosomes toward the opposite ends of the cell. Go to Section:

  7. Figure 11-17 Meiosis II Section 11-4 Meiosis II Prophase II Metaphase II Anaphase II Telophase II Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original. The chromosomes line up in a similar way to the metaphase stage of mitosis. The sister chromatids separate and move toward opposite ends of the cell. Meiosis II results in four haploid (N) daughter cells. Go to Section:

  8. Mitosis 1 division 2 daughter cells Exact copies of parent cells Diploid to diploid Purpose Growth Repair Asexual reproduction Meiosis 2 divisions 1st separates pairs 4 daughter cells Each unique Diploid to haploid Purpose Make gametes/ sex cells Leads to genetic variation due to crossing over Mitosis vs Meiosis

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