Meiosis<br />
What is it?<br />Mitosis occurs, producing two identical daughter cells<br />Only eukaryotic cells<br />In humans, all cel...
Where does it happen?<br />Made in reproductive organs<br />Males: testes  sperm<br />Females: ovaries  ova (eggs)<br />...
Creation of offspring <br />Fertilization<br />23 + 23 = 46<br />n + n = 2n<br />
Chromosomes<br />Humans contain 23 pairs of chromosomes (46 total)<br />Half from each parent<br />Pairs 1 through 22 are ...
Abnormalities<br />Nondisjunction- “failure to separate”<br />Trisomy: three of one type of chromosome<br />Trisomy 21: Do...
Meiosis<br />Serves to halve the number of chromosomes, creating gametes<br />In humans:<br />Male gametes – 4 haploid spe...
Meiosis I<br />Separates homologous pairs<br />
Crossing OverIncreases Genetic Variability<br />
Meiosis II<br />No duplication of chromosomes between Meiosis I & II<br />Meiosis II separates sister chromatids<br />
Meiosis II Results<br />Four daughter cells<br />Contain half as many (n) chromosomes as parent (2n)<br />Each cell is gen...
Meiosis in Humans<br />Formation of gametes<br />Males: Spermatogeneis<br />
Meiosis in Humans<br />Formation of gametes<br />Females: Oogeneis<br />Meiosis I<br />1 diploid cell<br />1 polar body<br...
Genetic Variations<br />Crossing over<br />Shuffle genes on chromosomes<br />Independent assortment of homologous pairs<br...
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Meiosis

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Honors Biology class PPt on the process of meiosis; used following Mitosis

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  • Circle 23rd pair: Sex chromosomes X &amp; Y (male; or XX female)
  • Ends with 4 sperm containing 23 chromosomes (n); contain either an X or YSeveral hundred million (200 000 000) sperm are produced each day
  • Most of the Cytoplasm is placed in one cell; 1 in 4 is viable; all XsAt birth each female carries a lifetime supply of developing oocytes, a total of 400-500 eggs
  • Meiosis

    1. 1. Meiosis<br />
    2. 2. What is it?<br />Mitosis occurs, producing two identical daughter cells<br />Only eukaryotic cells<br />In humans, all cells but one type<br />Involve diploid cells (2n)<br />Humans reproduce sexually<br />Sex cells = gametes = sperm & egg<br />Meiosis is the making of gametes<br />
    3. 3. Where does it happen?<br />Made in reproductive organs<br />Males: testes  sperm<br />Females: ovaries  ova (eggs)<br />Gametes contain 23 chromosomes <br />Haploid cells (n)<br />Mitosis involves the halving of the normal chromosome number<br />
    4. 4. Creation of offspring <br />Fertilization<br />23 + 23 = 46<br />n + n = 2n<br />
    5. 5. Chromosomes<br />Humans contain 23 pairs of chromosomes (46 total)<br />Half from each parent<br />Pairs 1 through 22 are <br /> homologous pairs<br />Same size<br />Carry genes for same traits<br />Not identical<br />
    6. 6.
    7. 7. Abnormalities<br />Nondisjunction- “failure to separate”<br />Trisomy: three of one type of chromosome<br />Trisomy 21: Down Syndrome<br />Monosomy: one of one type of chromosome<br />Klinefelter’s<br />XXY (23rd pair)<br />Turner’s Syndrome <br />XO (23rd pair)<br />
    8. 8. Meiosis<br />Serves to halve the number of chromosomes, creating gametes<br />In humans:<br />Male gametes – 4 haploid sperm<br />Female gametes – 1 haploid egg, 3 polar bodies<br />Meiosis I & Meiosis II<br />
    9. 9. Meiosis I<br />Separates homologous pairs<br />
    10. 10. Crossing OverIncreases Genetic Variability<br />
    11. 11.
    12. 12.
    13. 13.
    14. 14. Meiosis II<br />No duplication of chromosomes between Meiosis I & II<br />Meiosis II separates sister chromatids<br />
    15. 15.
    16. 16. Meiosis II Results<br />Four daughter cells<br />Contain half as many (n) chromosomes as parent (2n)<br />Each cell is genetically different<br />Fertilization restores chromosome number to 2n<br />
    17. 17. Meiosis in Humans<br />Formation of gametes<br />Males: Spermatogeneis<br />
    18. 18. Meiosis in Humans<br />Formation of gametes<br />Females: Oogeneis<br />Meiosis I<br />1 diploid cell<br />1 polar body<br />Meiosis II<br />1 haploid gamete<br />3 haploid polar bodies<br />Result<br />1 egg<br />
    19. 19. Genetic Variations<br />Crossing over<br />Shuffle genes on chromosomes<br />Independent assortment of homologous pairs<br />Arrange randomly on metaphase plate<br />223 (or 8 million) possibilities<br />Random fertilization<br />8 million egg x 8 million sperm = 64 trillion zygote<br />

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