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BIO201A Cell Biology Lecture 37 Monday 04/23/07

BIO201A Cell Biology Lecture 37 Monday 04/23/07. Important Announcements:. Friday, April 27, will be a review of the lab material.

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BIO201A Cell Biology Lecture 37 Monday 04/23/07

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  1. BIO201A Cell Biology Lecture 37 Monday 04/23/07

  2. Important Announcements: • Friday, April 27, will be a review of the lab material. • Monday, April 30, will be the last day of classes and will be carried out as a recitation. No new material will be presented. If you have questions about the lecture material, that is the time to ask about it. • Next exam will be the Final. 34 questions over section 3 and 14 lab questions. This is 48 total questions worth 140 total points. • Final exam is May 8th, 11:45AM to 2PM in four rooms: NSC 201 (lab sections A1-A4) NSC 218 (lab sections A5-A8) Norton 112 (lab sections A9-A12) OBrian 109 (lab sections A13-A16). Please note which room you will need to attend.

  3. Aneuploidy • Autosomal polyploidy. This is usually fatal except in the case of trisomy 21 (three chromosome #21) 2. Autosomal monosomy. Only one of the autosomes instead of two. This is usually fatal • Sex chromosome polyploidy. XXY is male with Kleinfelter’s syndrome XYY is male and was previously thought to have criminal tendencies because of being “too male” 4. Sex chromosome monosomy. XO is female with Turner syndrome All of these are caused by nondisjunctions during meiosis

  4. Aneuploidy in a cancer cell

  5. Cross-over recombination and chiasmata

  6. Two sources of genetic variability in Meiosis: • Crossing over and recombination. This happens in pacytene of prophase I • Independent Assortment of genetic traits (maternal and paternal) This happens in Anaphase I of meiosis What does this do? It produces genetic diversity

  7. Recombination 20_07_recombination.jpg Crossing-over and recombination occurs between non-sister chromatids in pachytene

  8. Chiasmata in Diplotene phase of meiotic prophase I chiasmata Chiasmata are covalent linkages between two non-sister chromatids. This helps to keep bivalents together after cohesion linkages are broken

  9. Segregation of chromatids modified by recombination 20_08_Chiasmata.jpg

  10. The chromatids of each gamete are different in this case 20_09_kinetochore_pull.jpg The DNA sequences of each chromatid is different. Each gamete can get different genetic information.

  11. Independent Assortment Recombination 20_11_reassortment.jpg

  12. Different strategies for mitosis and meiosis

  13. Gametic or terminal

  14. Plants, Sporic or intermediate fertilization Pollen (1n) + Egg (1n) 2n zygote mitosis sporophyte 2n meiosis Spores (haploid gametophytes) 1n 1n Fungi. Zygotic or initial 1n 1n Haploid Fertilization Mitosis 2n Meiosis 1n 1n Haploid adults

  15. Differentiation THEN Primary spermatocytes(2n4x4c) Primary oocyte (2n4x4c) Meiosis I Meiosis I Secondary oocyte (1n2x2c) Secondary spermatocyte(1n2x2c) Meiosis II Meiosis II Spermatids (1n1x1c) Differentiation Polar body (1n1x1c) Egg (1n1x1c) Sperm cells (1n1x1c)

  16. Summary • Mitosis produces daughter cells with the same genotype as the mother cell No genetic segregation or independent assortment in mitosis • Meiosis produces cells with different mixtures of maternal and paternal genes because of: Independent assortment Genetic recombination Independent assortment and recombination happen in meiosis, not mitosis

  17. Cloning animals nextFrom genetic variation to genetic uniformity

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