Chapter 7: Human Inheritance

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Chapter 7Human Inheritance

• Section 7-3
• Human Genetic Disorders

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Autosomal Genetic Disorders

• Most genetic disorders
• Genes located on autosomes
• Most are recessive such as
• Cystic fibrosis
• Tay-Sachs disease
• Sickel Cell Anemia
• Phenylketonuria (PKU)
• Some are dominant Huntingtons Disease,
  Achondroplasia

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Galactosemia

• Recessive genetic disorder
• Unable to digest galactose because missing or
  have low quantities of a certain enzyme
• Affects 1 in every 50 to 70,000
• Causes mental disabilities, enlarged liver,
  kidney failure
• No cure, patients must restrict lactose/galactose
  in diet

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Chromosome Number Disorders

• Individuals have an abnormal number of
  chromosomes
• Caused by nondisjunction, which is the failure of
  chromosomes to separate properly in meiosis (sex
  cells have an abnormal number of chromosomes)
• Nondisjunction

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Down Syndrome

• AKA Trisomy 21- Extra copy of the 21st chromosome
• Results in heart/circulatory problems, a weakened
  immune system, and mental retardation that varies
  in severity
• In the US, 1/800 are born with it
• Increased risk with age of mother if mother is
  gt45, risk is 6

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Chromosome Number Disorders

• Others include
• Edwards Syndrome
• Turners Syndrome
• Kleinfelters Syndrome

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Down Syndrome Karyotype
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Other Chromosome Problems

• Chromosome deletions a piece of a chromosome is
  broken off and lost during meiosis
• Chromosome translocations a piece that has
  broken off one chromosome and gets reattached to
  another chromosome

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Prenatal Diagnosis

• Amniocentesis involves withdrawing a small amount
  of fluid from the sac surrounding the developing
  fetus, where cells can be checked for
  abnormalities
• Chorionic villus sampling involves taking tissue
  surrounding the fetus
• Fetal blood sampling draw blood from fetus
  (most risk)

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Prenatal Diagnosis