Genes and Disease: Defects, Quirks, and Compromises

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Chapter 7

• Genes and Disease Defects, Quirks, and
  Compromises

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What Are Genes?

• Units of inheritance that determine hereditary
  traits.
• Located on chromosomes.
• 23 pairs of chromosomes.
• A, C, G, T
• A-T C-G
• Human genome project
• 93 of DNA codes for proteins.
• 7 of human genes are different for every
  individual.

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Genetic Defects

• Error during transcription and translation
• Chemical damage
• Ionizing radiation

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Genetic Diseases

• Caused by dominant or recessive traits
• Genotype and phenotype
• Huntingtons disease
• Sickle-cell anemia
• Cystic fibrosis
• Tay-Sachs disease
• Myopia

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Huntingtons Disease

• Caused by one dominant gene
• Memory loss, muscles stop working
• Easily passed on to offspring
• Gene found on chromosome 4

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Sickle-cell Anemia

• Heterozygous (Aa).
• Changes hemoglobin structure which prevents
  malaria because it quickly removes infected
  genes.
• Homozygous (AA).
• Have sickle-cell anemia which causes irregular
  red blood cells.
• Do not have resistance to malaria.
• Short lifespan.
• Heterozygous advantage.

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Tay-Sachs Disease

• Heterozygous protects against tuberculosis
• Homozygous individual dies
• Heterozygous advantage

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Myopia

• Genetic quirk
• Causes nearsightedness
• Different parts of the eye grow at different
  times
• Eye should stop growing when vision is no longer
  blurry
• Genes cause eye to keep growing
• Influenced by environment

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T-locus Gene

• Found in mice
• 2 copies is lethal
• 1 copy is passed to 90 of offspring
• Gene benefits, mouse does not

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Summary

• Genes are the building blocks for the body.
• Genetic defects cause different diseases.
• Recessive advantage.
• Sickle-cell anemia.
• Tay-sacs disease.
• Environmental influence myopia would not occur
  without genetic defect and environmental
  influence.
• Gene benefits.
• Huntingtons disease.
• T-locus gene.

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