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NOTES 24 – Genetic Disorders and Hereditary Diseases

NOTES 24 – Genetic Disorders and Hereditary Diseases. What is a genetic disorder?. A genetic disorder is a condition caused by any abnormality in a person’s genes or chromosomes Genetic disorders have 2 main causes. Cause #1.

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NOTES 24 – Genetic Disorders and Hereditary Diseases

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  1. NOTES 24 – Genetic Disorders and Hereditary Diseases

  2. What is a genetic disorder? • A genetic disorder is a condition caused by any abnormality in a person’s genes or chromosomes • Genetic disorders have 2 main causes

  3. Cause #1 • An error during meiosis causes a sperm cell or an egg cell to have some defect. • If one of these gametes is involved in fertilization, it usually results in miscarriage, but in a few cases, a baby will develop and be carried to term with a genetic disorder • EX. Down Syndrome is caused by an extra 21st chromosome in the sperm or egg cell

  4. Cause #2 • A defective gene present in one or both of the parents is inherited directly by the child causing a disorder • These kinds of disorders are calle hereditary diseases and follow the same rules of inheritance as other human traits

  5. Hereditary Diseases Caused by Dominant Genes • Only one copy of the gene (from either parent) is needed for a person to have the disease • A person with a dominant hereditary disease usually has at least one affected parent • Parents have a 50% chance of passing these types of diseases to children

  6. Ex. Huntington’s Disease • Caused by the inheritance of a dominant gene • Affects the nervous system • Produces incorrect protein that eventually leads to destruction of brain cells • Symptom’s include abnormal body movements, lack of coordination, impaired mental abilities and altered personality • Patients generally live 15 to 20 years after the appearance of the first symptoms • Currently no cure

  7. Hereditary Diseases Caused by Recessive Genes • Two copies of the defective gene must be inherited (one from each parent) • Affected persons usually have two non-affected parents who are carriers • Two carrier parents have a 25% chance of having a child with the disease

  8. Ex. Sickle-Cell Anemia • Caused by the inheritance of two recessive genes • Causes red blood cells to be abnormally shaped • Cells may stick to each other or become stuck in blood vessels preventing oxygen flow which may lead to organ damage or stroke • Individuals are often well, but experience painful, possibly fatal attacks from time to time

  9. Sickle Cell Anemia

  10. Hereditary Disease Caused by Sex-Linked Recessive Genes • Caused by defective genes carried on the X chromosome • Males affected more than women • Males inherit one defective gene on X from mother to have disorder • Females only affected if they inherit 2 defective genes (one from each parent)

  11. Ex. Hemophilia • Caused by the inheritance of one recessive gene on the X (males) or two recessive genes on both X’s (females) • Affects blood – blood does not clot • Leads to severely increased risk of bleeding from common injuries • Potentially fatal

  12. Hemophilia

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