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MEIOSIS & SEXUAL REPRODUCTION

MEIOSIS & SEXUAL REPRODUCTION. 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. TERMINOLOGY TO KNOW.

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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

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