Genetic disorders are health conditions caused by changes in genes — also called mutations or variants. Genes are the parts of DNA in your cells that carry instructions for how your body grows, develops and works. Many genes tell the body how to make proteins, which it needs to function.
How a gene change causes disease
A disorder can result when a variant changes how a protein is made, so the protein works poorly or isn't made at all. But not all gene changes cause disease — many have no effect. Sometimes, though, even a small change in DNA matters.
| Variant | |
|---|---|
| Inherited (germline) | passed down from your parents, through the egg or sperm cell |
| Non-inherited (somatic) | arises during your lifetime, for example from harmful chemicals or the sun's ultraviolet (UV) rays |
Types of genetic disorders
| Type | Cause | Example |
|---|---|---|
| Single-gene | a change in one gene | sickle cell anemia (always the same gene); Charcot-Marie-Tooth disease (a variant in any one of many genes) |
| Chromosomal | missing, extra or altered chromosomes — the structures that carry genes — changing their number or structure | Down syndrome, from an extra copy of chromosome 21 |
| Complex (multifactorial) | changes in many genes, each adding risk, together with lifestyle and environment — exercise, diet, pollution | colon cancer |
How disorders are inherited
Some conditions run in families in one of several patterns, depending on the gene:
| Pattern | |
|---|---|
| Dominant | one changed gene is enough to cause the condition |
| Recessive | it takes two changed copies — one from each parent |
| X-linked | the gene is on the X chromosome; these conditions often affect males more |
| Mitochondrial | passed down by the mother |
Diagnosis
Your provider may look for a genetic condition through a physical exam, your medical history, your family health history, and lab tests, including genetic testing.
Sources
Based on "Genetic Disorders," MedlinePlus, U.S. National Library of Medicine; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from medlineplus.gov
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