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AP Bio: Wednesday, 3.9.11 Sexual Reproduction & Meiosis

AP Bio: Wednesday, 3.9.11 Sexual Reproduction & Meiosis. Homework due tomorrow: PS 14 and completed Embryonic Development packet (stapled together) Also – short quiz tomorrow – study the problem set! Do Now: On the handout… Today’s Goals: Explain the key steps of sexual reproduction

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AP Bio: Wednesday, 3.9.11 Sexual Reproduction & Meiosis

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  1. AP Bio: Wednesday, 3.9.11Sexual Reproduction & Meiosis • Homework due tomorrow: • PS 14 and completed Embryonic Development packet (stapled together) • Also – short quiz tomorrow – study the problem set! • 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) 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. AP Bio: Thursday, 3.10.11Quiz: Mitosis & Embryology • Homework for Monday: • PS 15 #1, 2 and one other question (bring notes for the other question) • Complete Lab 3B • Do Now: • Hand in PS 14 plus the Embryology worksheet • Get work back (Test 8 and PS 13) • Get a PS 15 and sign up for one question other than #1-2 • Today’s Goals / Agenda: • Quiz your knowledge of mitosis and embryology • Complete Lab 3B

  9. AP Bio: Tuesday, 3.15.11Details of Meiosis • Homework: • Completed Transformation Lab Report due tomorrow • PS 15 due Thursday • Do Now: (please write down your answers) • What is the overall goal of meiosis? • What are 3 key differences between mitosis and meiosis? • Today’s Goals: • Explain how meiosis creates genetic diversity between gametes • Agenda: • Special Thursday? • AP Exam Sign-Up • Lecture/Discussion • Work time on assigned PS 15 questions • Presentation on PS 15 #4

  10. 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

  11. 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

  12. Stages of Meiosis

  13. Meiosis generates genetic diversity between gametes: Two Ways 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?

  14. Meiosis generates genetic diversity between gametes: Two Ways 2. 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.

  15. AP Bio:Wednesday, 3.16.11Details of Meiosis • 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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