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Genetic Disorders

A genetic disorder is a disease that stems from a problem in the genetic makeup of an organism. The abnormality can be a result of heredity, of unexplained genetic mutation or of accidental gene duplication. A majority of the thousands of genetic diseases found in humans happen infrequently. The disorders are broken down into four categories: single gene, multifactorial, chromosomal and mitochondrial.

Single gene disorders, also called monogenic, happen when one gene mutates and causes irregular protein functions. Examples are cystic fibrosis (which is the most common), sickle cell anemia, or even color blindness.

Multifactorial disorders, also called polygenic, are a more complex combination of larger scale genetic mutation and the effects of lifestyle or environment. This is the most common category of chronic genetic disorder. Examples are diabetes, heart disease and epilepsy. Although these diseases often affect a number of people in the same family, it is not possible to pre-determine who will be afflicted.

Chromosomal disorders are caused by abnormalities of the chromosomes in the nucleus of cells, manifested either as a lack, surplus or breakage of the required chromosomal number for proper development. Down Syndrome, for example, is a disease due to surplus. Mitochondrial disorder is the most rare category. It results from the mutation of the nonchromosal DNA of cellular mitochondria.

Web Resources On Genetic Disorders

Wikipedia: Genetic Disorders
Genetic Disease Information

Book Resources On Genetic Disorders

The Encyclopedia of Genetic Disorders and Birth Defects by James Wynbrandt and Mark D. Ludman
Mendelian Inheritance in Man: A Catalog of Human Genes and Genetic Disorders by Victor A. McKusick, et al

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