Medical Health Encyclopedia

Autosomal recessive

CHANCES OF INHERITING A TRAIT

For an autosomal recessive disorder: When both parents are carriers of an autosomal recessive trait, there is a 25% chance of a child inheriting abnormal genes from both parents, and therefore of developing the disease. There is a 50% chance of each child inheriting one abnormal gene (being a carrier).

In other words, if it is assumed that 4 children are produced, and both parents are carriers (neither exhibits any disease), the STATISTICAL expectation is for:

• 1 child with 2 normal chromosomes (normal)
• 2 children with 1 normal and 1 abnormal chromosome (carriers, without disease)
• 1 child with 2 abnormal chromosomes (has the disease)

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This does not mean that children WILL necessarily be affected. It does mean that EACH child has a one in four chance of inheriting the disorder and a 50:50 chance of being a carrier.

RELATED TOPICS

Autosomal dominant

Genetic counseling and prenatal diagnosis

Sex-linked dominant

Sex-linked recessive

For detailed information, see heredity and disease (genetics).

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