Human Genetic Disorders

  1. Many genes linked to certain diseases have been discovered.
  2. Phenylketonuria
  3. People w/ PKU lack enzyme needed to break down phenylalanine, an amino acid found in milk and many other foods.
  4. If a newborn baby builds up too much phenylalanine, it could lead to severe learning disabilities.
  5. Tests candiagnose& patients can be placed on specialized diets to prevent the effects of PKU.
  6. Can also cause lack of skin pigment and sterility.
  7. Caused by recessive allele.
  1. Other recessive allele disorders…
  1. TAY-SACHS DISEASE
  2. Caused by recessive allele found in mostly Jewish families with ancestry from eastern/central Europe.
  3. Causes breakdown of nervous system and death within the first few years of life.
  4. Accumulates lipids in the brain, learning disabilities, and blindness.
  5. Currently is no treatment, but tests can diagnose children.
  1. ALBINISM
  2. Lack of pigment in skin, hair, and eyes.
  1. CYSTIC FIBROSIS
  2. Excess mucus in lungs, digestive tract, and liver.
  3. Usually found among populations w/ancestry from northern Europe.
  4. Approx. 1:28 white Americans carry one recessive allele found on chromosome 7.
  5. Death in childhood is common, most people not living past their 20’s.
  1. Dominant allele disorders.
  1. ACHONDROPLASIA
  2. One of the many forms of dwarfism.
  3. Proportional limbs to trunk.
  1. HUNTINGTON’S DISEASE
  2. Progressive loss of muscle control and mental functions.
  3. People who have this disease usually show no symptoms until their 30’s and 40’s.
  4. X-linked, more common in males
  1. HYPERCHOLESTEROLEMIA
  2. Excess of cholesterol in blood
  3. Can lead to heart diseases & heart attacks.
  1. Co-dominant allele disorders.
  2. SICKLE-CELL ANEMIA
  3. Major disease in the US & Africa.
  4. Infects people who can track their ancestry back to west-central Africa.
  5. At least 1:12 African Americans are at least heterozygous for the disorder. (Sickle-Trait)
  6. Loses ability to produce certain amino acids, causing lack of oxygen-trapping protein HEMOGLOBIN.]
  1. Because lack of hemoglobin, the blood cells collapse and become sickle-shaped.
  2. Causes the blood cell to have a shorter life, and can clog in narrow capillaries.
  3. People who are heterozygous produce both normal and sickle cells.
  4. People who have sickle-cell are resistant to malaria.
  5. Possible evolutionary trait?