Lecture 4 exam 3

Lecture 4 exam 3 - Biology 313 Lecture 26 Down Syndrome...

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Biology 313 Lecture 26 Oct 27, 2010
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Down Syndrome phenotype first described by John Down, Brit. physician (1866): most common genetic mental handicap Trisomy 21 first described in 1959 Complex genetics: multiple genes on chrom. 21 are responsible for Down syndrome
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Trisomy 21 = Primary Down syndrome Due to nondisjunction of chromosome 21 during meiosis (usually, meiosis is defective in the mother) Primary Down Syndrome
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Due to Robertsonian translocation between chromosomes 14 (or 15) and 21 Familial Down Syndrome
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Translocation Carrier (Walk through 9-23) Translocation carriers are normal but have an increased risk of having children with Down syndrome
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Aneuploidy and Maternal Age Female mammals are born with their primary oocytes suspended in prophase I of meiosis; meiosis is completed upon ovulation and after fertilization Hypothesis: Components of the spindle might break down during the long arrest of meiosis, enhancing the chances of nondisjunction
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Chromosome mutations Variations in number and/or structure of chromosomes Three classes: Rearrangements Aneuploids Polyploids
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This note was uploaded on 10/06/2011 for the course BIO 313 taught by Professor Rodermel during the Spring '11 term at Iowa State.

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Lecture 4 exam 3 - Biology 313 Lecture 26 Down Syndrome...

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