When%20Meiosis%20Goes%20Wrong: - PowerPoint PPT Presentation

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When%20Meiosis%20Goes%20Wrong:

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When Meiosis Goes Wrong: Non-Disjunction Normal Meiosis In Anaphase I, homologous chromosomes split up and each one goes to a pole. In Anaphase II, the chromosome ... – PowerPoint PPT presentation

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Title: When%20Meiosis%20Goes%20Wrong:


1
When Meiosis Goes Wrong
  • Non-Disjunction

2
Normal Meiosis
  • In Anaphase I, homologous chromosomes split up
    and each one goes to a pole.
  • In Anaphase II, the chromosome break in two and
    each chromatid goes to a pole.

3
Non-Disjunction
Nondisjunction of homologous chromosomes in
meiosis I
  • Sometimes, in Anaphase I, the chromosome pairs
    DONT split
  • 2 cells with an extra chromosome, 2 missing a
    chromosome
  • In Anaphase II, if a chromosome doesnt split in
    two
  • 2 normal cells, 1 with too many chromosomes, 1
    with not enough.

4
So?
  • When non-disjunction happens, the egg or the
    sperm produced has the wrong number of
    chromosomes.
  • If this egg/sperm fertilizes, the baby will have
    the wrong number of chromosomes.
  • This child often suffers from health problems and
    learning disabilities.

5
To Diagnose Non-Disjunction
Normal Male
  • Doctors use a karyotype chart, which shows all
    your chromosomes.
  • A normal karyotype has 46 chromosomes (23
    pairs)
  • Males have an X and a Y, females have 2 X
    chromosomes.

Normal Female
6
Examples of Disorders
  • Downs Syndrome
  • 3 copies of chromosome number 21
  • Heart defects, poor mouth development, learning
    disabilities
  • Shortened life expectancy

7
Examples of Disorders
  • Trisomy 13
  • 3 copies of chromosome number 13.
  • Major learning disabilities, small head, mouth
    deformities
  • Few survive to adulthood

8
Examples of Disorders
  • Turners Syndrome
  • Only 1 copy of the X chromosome.
  • Short, female, webbed neck, infertile, heart
    defects.
  • Normal life expectancy and intelligence.
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