Genetic Disorders

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Genetic Disorders
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Genetic Disorders

• Caused by a harmful mutation (physical change of
  gene)
• Mutation originally occurs in gamete and is
  passed to future generations (inherited)
• The gene that is mutated determines the disease.
  The allele that is mutated determines its
  inheritance pattern

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Autosomal Recessive

• Mutation produces a recessive allele
• Genotypes
• CC unaffected
• Cc carrier (unaffected)
• cc affected
• Examples Cystic Fibrosis, Tay-Sachs, Sickle Cell
  Anemia (inc. dominance)

If two unaffected parents have a child with
cystic fibrosis, what are their genotypes?
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Autosomal Recessive Pedigree
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X-linked Recessive

• Mutation produces a recessive allele on the X
  chromosome.
• Genotypes
• Examples Hemophilia A, Red-green Color Blindness

Female Male
XHXH - unaffected XHY - unaffected
XHXh carrier (unaffected) XhY - affected
XhXh - affected No male carrier
Dianes father and brother have hemophilia. There
is no family history of hemophilia in Craigs
family. What is the probability that their child
will have hemophilia. What if they have a girl? A
boy?
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X-linked Recessive Pedigree
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Autosomal Dominant

• Mutation produces a dominant allele
• Genotypes
• HH affected
• Hh affected
• hh unaffected
• Examples Huntington Disease

Although Huntington disease is very rare in the
total population, it appears at a rate of 50
percent in affected families. Explain this in
genetic terms.
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Autosomal Dominant Pedigree
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Chromosomal Disorders

• /- chromosomes
• 1 extra trisomy
• 1 missing monosomy
• Caused by nondisjunction failure of one or more
  chromosome pairs to separate during meiosis
• Examples Down Syndrome, Klinefelters Syndrome,
  Turners Syndrome

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Nondisjunction can occur during Meiosis I or
Meiosis II
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Down Syndrome (Trisomy 21)
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Turner Syndrome (45, X)
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Klinefelter Syndrome (47, XXY)