Patterns of Human Inheritance

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Patterns of Human Inheritance
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Complex Inheritance and Human Heredity
Recessive Genetic Disorders

• A recessive trait is expressed when the
  individual is homozygous recessive for the trait.

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Complex Inheritance and Human Heredity
Cystic Fibrosis

• Affects the mucus-producing glands, digestive
  enzymes, and sweat glands

• Chloride ions are not absorbed into the cells.

• Without sufficient chloride ions in the cells, a
  thick mucus is secreted.

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Complex Inheritance and Human Heredity
Albinism

• Caused by altered genes, resulting in the absence
  of the skin pigment melanin in hair and eyes

• White hair

• Very pale skin

• Pink pupils

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Complex Inheritance and Human Heredity
Tay-Sachs Disease

• Caused by the absence of the enzymes responsible
  for breaking down fatty acids called gangliosides

• Gangliosides accumulate in the brain, inflating
  brain nerve cells and causing mental
  deterioration.

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Complex Inheritance and Human Heredity
Galactosemia

• Recessive genetic disorder characterized by the
  inability of the body to digest galactose.

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Complex Inheritance and Human Heredity
Dominant Genetic Disorders

• Huntingtons disease affects the nervous system.

• Achondroplasia is a genetic condition that causes
  small body size and limbs that are comparatively
  short.

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Complex Inheritance and Human Heredity
Basic Patterns of Human Inheritance
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Human Genetics

• Difficulties with human genetics
• Takes a long time to reach reproductive maturity
• Relatively few offspring
• Unethical to arrange matings between
  individuals with desired genotypes
• Pedigree a graphic representation of genetic
  inheritance, a families phenotypic history
• Made up of set of symbols

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Pedigree Analysis
Symbols
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Pedigree Analysis

• Family Trees
• Generations are numbered on the left with roman
  numerals
• Siblings are numbered in birth order

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Pedigree Analysis
Complex Inheritance and Human Heredity
Inferring Genotypes

• Knowing physical traits can determine what genes
  an individual is most likely to have.

Predicting Disorders

• Record keeping helps scientists use pedigree
  analysis to study inheritance patterns, determine
  phenotypes, and ascertain genotypes.