Presymptomatic testing

Definition

• Genetic analysis of an asymptomatic or unaffected individual who is at risk of a specific genetic disorder.

Genetic testing and ethics

Pronunciation

PREE-simp-toh-MA-tik TES-ting

Other names

• Carrier screening, carrier testing, genetic testing, genetic screening

Population screening

• Presymptomatic screening is really a specific type of genetic screening, that we apply to a large population of people who don't have any symptoms of the disease, as they can be asymptomatic carriers.
• The asymptomatic carriers may be at risk for passing it along to their children or potentially may develop the disease later in their life.

Punnett Square Genetic Carriers

Conditions screened

• Both autosomal recessive conditions and X-linked recessive conditions are screened.

Who are carriers?

• Parents of children with genetic disease might not be symptomatic as they might be just carriers.
• Children inherit two copies of each gene, one from each parent. For some genetic diseases, the baby will only have the disease if both copies of the gene related to the disease do not work properly.
• Each parent has one copy of the gene that works properly and one that does not.
• If the baby inherits both non-working copies of the gene or affected gene, the baby has the disease.
• In this situation, the parents are “carriers” for the disease, meaning that they don’t have the disease themselves but can have children with it.

Autosomal recessive inheritance - Carriers

Examples

• Some of the examples of diseases that we do carrier testing for are things like cystic fibrosis, Tay-Sachs disease, sickle cell disease, hemophilia, and Fragile X syndrome.

Latest articles - Presymptomatic testing

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Presymptomatic testing on Wikipedia

• Wikipedia's article on Presymptomatic testing

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