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MEIOSIS & SEXUAL REPRODUCTION PowerPoint Presentation
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MEIOSIS & SEXUAL REPRODUCTION

MEIOSIS & SEXUAL REPRODUCTION

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MEIOSIS & SEXUAL REPRODUCTION

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  1. MEIOSIS & SEXUAL REPRODUCTION

  2. OBJECTIVES • Understand the meaning of “SEX” • Understand distinction between meiosis and mitosis • Understand the processes that take place during meiosis • Be familiar with relevant vocabulary presented in class

  3. TERMINOLOGY TO KNOW Homologous chromosomes (homologs): Diploid: Haploid: Sister Chromatids:

  4. SEXUAL REPRODUCTION • Fertilization: • A male & female gamete fuse • Egg + sperm 

  5. SEXUAL REPRODUCTION August Weismann’s (1887) Hypothesis: • Gamete production involves distinctive type of cell division • Later confirmed by cell biologists

  6. MEIOSIS Special Type of Cell Division was Termed Meiosis: • Results in production of sex cells • Takes place in reproductive organs of multicellular organisms • Plants: • Animal:

  7. MEIOSIS Overall Goal: • Reduce chromosomes in half • Haploid daughter cells function as gametes • Sexual reproduction can then occur

  8. BUT BEFORE REDUCTION… • Chromosomes are doubled (S Phase) • Same as mitosis

  9. MEIOSIS Two Parts: • Meiosis I: • Meiosis II:

  10. MORE TERMINOLOGY TO KNOW Crossing Over • The exchange of maternal & paternal sections of homologous chromosomes • Results in shuffling of genome

  11. MEIOSIS I 1.Non-sister chromatids of a homologous pair cross over & exchange DNA 2. Homologous pairs line up at cell equator • Homologous • chromosomes • separate 4. Same as mitosis

  12. MEIOSIS II 6. Chromosomes line up at cell equator 7. Sister chromatids separate 8. Cell division results in 4 daughter cells 5. Chromosomes begin moving to middle of cell.

  13. PRODUCT OF MEIOSIS: GAMETES • Each gamete gets one member (1 chromatid) of each homologous pair

  14. FERTILIZATION RESTORES FULL SET OF CHROMOSOMES Female gamete Male gamete fertilization

  15. PRODUCT OF FERTILIZATION: A DIPLOID ZYGOTE • Fertilization restores the diploid number of chromosomes • When gametes fuse: gamete (23) + gamete (23) 

  16. Mitosis: Meiosis: COMPARISON OF MITOSIS & MEIOSIS

  17. DIFFERENCE BETWEEN MITOSIS & MEIOSIS

  18. DIFFERENCE BETWEEN MITOSIS & MEIOSIS

  19. ADVANTAGES OF SEX • Sexual reproduction increases individual variation within a species • Asexual Reproduction (Mitosis): • Results in offspring = to parents • Sexual Reproduction (Preceded by Meiosis):

  20. ADVANTAGES OF SEX • Genetic diversity produces some organisms that are adaptable to non favorable conditions:

  21. DISADVANTAGES OF SEX • Sex Slows Rate of Reproduction! • Asexual Reproduction: • Sexual Reproduction:

  22. DISADVANTAGES OF SEX Asexual reproduction Sexual reproduction Generation 1 Generation 2 Generation 3

  23. DISADVANTAGES OF SEX Errors In Inheritance:

  24. DISADVANTAGES OF SEX Nondisjunction:

  25. DISADVANTAGES OF SEX • If fertilization occurs (after nondisjunction), a zygote with an abnormal number of chromosomes results:

  26. TRISOMY • Trisomy 21 (Downs Syndrome): • Symptoms Include:

  27. INCIDENCE OF TRISOMY 21AS A FUNCTION OF AGE OF MOTHER

  28. TRISOMY • Trisomy 13 • (Patau Syndrome) • Symptoms include:

  29. TRISOMY JACOBS MALE (XYY)

  30. Klinefelter • Syndrome (XXY) • Symptoms Include: TRISOMY

  31. TRISOMY • MetaFemale (XXX) • Symptoms Include:

  32. MONOSOMY • Turner Syndrome (XO) • Symptoms Include:

  33. ABNORMALITIES OF SEX CHROMOSOME NUMBER Jacobs Male Metafemale