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Errors in Meiosis

Errors in Meiosis. When Meiosis Goes Wrong. What’s a Mistake in Meiosis? . Too many or not enough chromosomes which can lead to genetic disorders Chromosomes can have errors. Mutations. When DNA is damaged or DNA is chan ged so that the code carried is now differen t

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Errors in Meiosis

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  1. Errors in Meiosis When Meiosis Goes Wrong

  2. What’s a Mistake in Meiosis? • Too many or not enough chromosomes which can lead to genetic disorders • Chromosomes can have errors

  3. Mutations • When DNA is damaged or DNA is changed so that the code carried is now different • Not all mutations are bad 

  4. Types of Errors

  5. 1. NON-DISJUNCTION

  6. Terms Used to Describe the type of Non-Disjunction • Aneuploidy – Means too few or too many chromosomes. • Monosomy - Having only 1 copy of a particular chromosome. • Example: Turner syndrome – missing X chromosome or possess an abnormal X chromosome • Polysomy – Having one or more extra sets of chromosomes. • Example: Down Syndrome – extra chromosome #21

  7. 2. CHROMOSOMAL ERRORS • Deletions:  Sections of DNA are missing • Duplications:  Sections of DNA are duplicated • Inversions: Sections of DNA are attached in reverse order • Translocations:  Sections of DNA are reattached to the wrong chromosome

  8. Errors are detected by analyzing the karyotype

  9. What is a Karyotype? • Photograph of chromosomes, usually done during metaphase • Shows 22 pairs of non-sex chromosomes and one pair of sex chromosomes • XX = girl • XY = boy

  10. http://www.bioteach.ubc.ca/Bio-industry/Xenon/graphics/karyotype.gifhttp://www.bioteach.ubc.ca/Bio-industry/Xenon/graphics/karyotype.gif

  11. It is possible to have trisomy of chromosomes 13, 15, 18, 21 & 22 • Unfortunately it is usually fatal if the embryo has trisomy of any of the other autosomal chromosomes

  12. With a partner, examine the karyotype on the next slide • Tell me: If this is a: a) non-disjunction b) chromosomal error(chromosome long/short) • How do you know?

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