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MISTAKES IN MEIOSIS

MISTAKES IN MEIOSIS. Nondisjunction. failure of homologous chromosomes to separate correctly during anaphase I or II of meiosis. Nondisjunction can lead to…. Makes gametes with one extra OR one less chromosome. monosomy. Monosomy  has 1 less chromosome

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MISTAKES IN MEIOSIS

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  1. MISTAKES IN MEIOSIS

  2. Nondisjunction • failure of homologous chromosomes to separate correctly during anaphase I or II of meiosis.

  3. Nondisjunction can lead to…. • Makes gametes with one extra OR one less chromosome

  4. monosomy • Monosomy has 1 less chromosome Ex. sperm (22) + egg (23) = baby (45)

  5. Example of monosomy • Turner’s Syndrome  45 chromosomes *Mother only gives 22 chromosomes *Father gives 23 chromosomes

  6. TURNERS SYNDROME

  7. trisomy • Trisomy has 1 extra chromosome Ex. sperm (23) + egg (24) = baby (47)

  8. EXAMPLE OF TRISOMY • Down’s Syndrome • extra chromosome #21

  9. Down syndrome karyotype

  10. Example of trisomy • Klinefelter’s Syndrome extra sex chromosome (#23)

  11. Klinefelter syndrome karyotype

  12. Polyploidy • When none of the homologous chromosomes separate the gamete stays diploid(2n) instead of separating and becoming haploid(n) • Ex. 2n gamete + n gamete = 3n baby (triploid) (abnormal) (normal) 2n gamete + 2n gamete = 4n baby (tetraploid)

  13. Polyploidy at work • Extra sets of chromosomes  polyploidy • Polyploidy is common in plants, but rare in animals (usually leads to death of the zygote in animals)

  14. Examples of Polyploidy Triploid seedless watermelon Octoploidy strawberries

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