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AP Bio: Thursday 3/15/12 Sexual Reproduction & Meiosis

AP Bio: Thursday 3/15/12 Sexual Reproduction & Meiosis. Homework due tomorrow: Lab 3B (Meiosis) Analysis Questions Do Now: On the handout… Today’s Goals: Explain the key steps of sexual reproduction Review key vocabulary terms Explain and model the steps and purpose of meiosis Agenda:

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AP Bio: Thursday 3/15/12 Sexual Reproduction & Meiosis

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  1. AP Bio:Thursday 3/15/12Sexual Reproduction & Meiosis • Homework due tomorrow: • Lab 3B (Meiosis) Analysis Questions • Do Now: • On the handout… • Today’s Goals: • Explain the key steps of sexual reproduction • Review key vocabulary terms • Explain and model the steps and purpose of meiosis • Agenda: • Lecture/Discussion • Lab 3B: Modeling Meiosis w/ Pipecleaners

  2. Asexual vs. Sexual Reproduction Asexual Reproduction One parent Parent and offspring are genetically identical (clones) Reproduce using MITOSIS (euks) or BINARY FISSION (proks) or by BUDDING or FRAGMENTATION Sexual Reproduction Two parents Offspring are genetically different from parents Reproduce using MEIOSIS (makes eggs and sperm) and FERTILIZATION (egg and sperm join)

  3. Sexual Reproduction Life Cycle

  4. Major Genetics Terms • Gene: • A section of DNA that holds instructions for making one protein • Ex: gene for hemoglobin protein • Alleles: • Different versions of a gene • Ex: normal hemoglobin allele vs. mutated hemoglobin allele • Chromosome: • A long strand of DNA, coiled and wrapped up, that contains many genes • Homologous Chromosomes: • A pair of chromosomes that contain the same genes but not necessarily the same alleles

  5. Major Genetics Terms (continued) • Diploid: • A cell that contains TWO COPIES of every chromosome (in homologous pairs) • All human body cells except gametes are diploid. • Haploid: • A cell that contains ONE COPY of every chromosome • Gametes are haploid.  • Gametes: • Egg or sperm cells, used in sexual reproduction. • Contain HALF the number of chromosomes as all other body cells (they are haploid) • Meiosis: The process of making gametes. • 1 Diploid cell  4 Haploid cells • Separates homologous chromosomes into different cells • Unlike in mitotic cell division, the resulting daughter cells are NOT identical

  6. Meiosis

  7. Watch the video…

  8. Lab 3B: Meiosis w/ Pipecleaners!

  9. AP Bio:Friday 3/16/12Details of Meiosis • Homework: • Take notes and be ready to present on your assigned problem set question • PS 15 due Wednesday 3/21/12 • Do Now: • Get a copy of PS 15 and adjust the date (sorry!) • Read questions 3-7 and pick one or more that you’re interested in • Today’s Goals: • Explain how meiosis creates genetic diversity between gametes • Agenda: • Lecture/Discussion: Details of Meiosis

  10. Start: Start: Meiosis I: Mitosis: Meiosis II: End: End:

  11. Start: Diploid Cell (46 Chromosomes in Humans) Start: Diploid Cell (46 Chromosomes in Humans) Meiosis I: chromosomes line up with homologous pairs, which then separate (sister chromatids stay together) Mitosis: chromosomes line up single file and sister chromatids split End: 4 Haploid Cells (23 Chromosomes in Humans) Cells different from starting cell (half the # of chromosomes) Meiosis II: sister chromatids split (like mitosis) End: 2 Diploid Cells (46 Chromosomes in Humans) Cells same as starting cell

  12. Summary of Meiosis

  13. Summary of Meiosis Gametes • DNA is replicated once • Chromosomes and cells are divided twice: • Meiosis I: Homologous chromosomes pair up and separate • Forms 2 haploid cells • Chromosomes still have sister chromatids • Meiosis II: Sister chromatids separate • Final result: 4 haploid gametes with HALF the number of chromosomes as the original cell

  14. Stages of Meiosis

  15. Two Ways meiosis generates genetic diversity between gametes:

  16. Two Ways meiosis generates genetic diversity between gametes: 1. Crossing over during Prophase I. One sister chromatidtrades a section of DNA with its homologous partner. Creates new combinations of alleles on chromosomes. Can happen at multiple places along the chromosome, allowing for a nearly infinite number of different gametes.

  17. Two Ways meiosis generates genetic diversity between gametes:

  18. Two Ways meiosis generates genetic diversity between gametes: 2. Independent alignment of homologous pairs during Metaphase I. A cell with 2 homologous pairs yields 4 possible gametes. How many are possible with 23 homologous pairs?

  19. Sexual Reproduction Generates Genetic Diversity in 3 Ways: • Meiosis: Independent Alignment of Homol. Chromosomes in Metaphase I • Meiosis: Crossing Over • Fertilization: Random Selection of the Diverse Egg and Sperm Cells generated by Meiosis

  20. Lab 3B Review…

  21. AP Bio:Tuesday 3/20/12Variations on Meiosis & Reproduction • Homework: • PS 15 due tomorrow. We WILL have class tomorrow @ 7:20 sharp. • Do Now: • Hand in Transformation Lab Report and get back other labs • Group #3 – get ready to present • Everyone else – what do you think are some differences between making eggs and making sperm? • Today’s Goals: • Apply knowledge of meiosis to… • Various interesting and weird reproductive situations • Explain Mendel’s Laws of Inheritance • Agenda: • PS 15 Presentations • Chapter 14 – Reading & Worksheet

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