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Genetic: Genetic Disorders

Genetic: Genetic Disorders

Genetic disorders are a group of lifelong diseases caused by abnormalities in genes or chromosomes that are present at the time that a baby is conceived. Genetic disorders may involve extra chromosomes (Down syndrome, Edwards syndrome, Patau syndrome, triple X syndrome, Klinefelter syndrome), a missing chromosome (Turner syndrome), or mutations in the parents' sperm or egg (fragile X syndrome, Huntington syndrome).

About 4,000 genetic disorders are known to exist. Most of these are very rare, affecting only one person in several thousand or several million. Cystic fibrosis, the most common genetic disorder in the United States, affects one child in every 3,900. However, about one American in every twenty carries the gene for the disease.

Genetic disorders vary in their inheritance patterns. In some disorders, like Huntington disease or Marfan syndrome, the child needs only one copy of the mutated gene to develop the disorder. In others, such as cystic fibrosis or sickle cell anemia, the child must inherit the defective

gene from both parents in order to have the disease. Some genetic disorders are caused by defective genes on the X or Y sex chromosomes.

SEE ALSO Achondroplasia; Cystic fibrosis; Down syndrome; Edwards syndrome; Fragile X syndrome; Huntington disease; Hutchinson-Gilford syndrome; Klinefelter syndrome; Marfan syndrome; Patau syndrome; Phenylketonuria; Sickle cell anemia; Thalassemia; Triple X syndrome; Turner syndrome; Xeroderma pigmentosum

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