Genetic disorder

A genetic disorder is a health problem caused by abnormalities in the genome. They are heritable, and may be passed down from the parents' genes to their children and to later generations. If a genetic disorder is present from birth, it is described as a congenital defect. Some defects only show up in later life.

The mutation responsible can occur spontaneously before the embryo develops, or it can be inherited from parents who are carriers of a faulty gene.

There are well over 6,000 known genetic disorders, and new genetic disorders are constantly being found. More than 600 genetic disorders are treatable. Around 1 in 50 people are affected by a known single-gene disorder, while around 1 in 263 are affected by a disorder caused by their chromosomes. Parts of a chromosome may be absent, or duplicated.

About 65% of people have some kind of health problem as a result of congenital genetic mutations. About 1 in 21 people are affected by a genetic disorder classified as "rare" (less than 1 in 2,000 people). Most genetic disorders are rare in themselves. They may affect one person in every several thousands or even millions. Sometimes they are relatively frequent in a population. If they are frequent, it suggests these recessive gene disorders give an advantage in certain environments when only one copy of the gene is present. Sickle cell anaemia is an example of this.

The same disease, such as some forms of cancer, may be caused by an inherited genetic condition in some people, by new mutations in other people, and by nongenetic causes in still other people. A disease is only called a genetic disease if it can be inherited at birth. The particular defect may only show up later in life.

Genetic Disorder Media

• Down Syndrome Karyotype.png

  Chromosomes in Down syndrome, the most common human condition due to aneuploidy. There are three chromosomes 21 (in the last row).

• Personal genomics gene therapy flowchart.png

  From personal genomics to gene therapy

• Autosomal recessive inheritance for affected enzyme.png

  Hereditary defects in enzymes are generally inherited in an autosomal fashion because there are more non-X chromosomes than X-chromosomes, and a recessive fashion because the enzymes from the unaffected genes are generally sufficient to prevent symptoms in carriers.

Related pages

• Birth defect
• List of genetic disorders
• Prenatal diagnosis