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Autosomal recessive

Genetics - autosomal recessive; Inheritance - autosomal recessive

Autosomal recessive is one of several ways that a genetic trait, disorder, or disease can be passed down through families.

An autosomal recessive disorder means two copies of a variant gene must be present in order for the disease or trait to develop.

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Most human beings have cells with 46 chromosomes. These consist of 2 chromosomes that determine what sex they are (X and Y chromosomes), and 22 pairs of nonsex (autosomal) chromosomes. Typically, males are "46,XY" and females are "46,XX."

Inheriting a specific disease, condition, or trait depends on the type of chromosome that is affected. The two types are autosomal chromosomes and sex chromosomes. It also depends on whether the trait is dominant or recessive.

A variation in a gene on one of the nonsex (autosomal) chromosomes can lead to an autosomal disorder.

Genes come in pairs. One gene in each pair comes from the egg, and the other gene comes from the sperm. Recessive inheritance means both genes in a pair must be a variant to cause disease. People with only one variant gene in the pair are called carriers. These people are most often not affected with the condition. However, they can pass the variant gene to their children.

CHANCES OF INHERITING A TRAIT

If you are born to parents who both carry the same autosomal recessive gene, you have a 25% (1 in 4) chance of inheriting the variant gene from both parents and developing the disease. You have a 50% (1 in 2) chance of inheriting one variant gene. This would make you a carrier.

In other words, for a child born to a couple who both carry the variant gene (but do not have signs of disease), the expected outcome for each pregnancy is:

• A 25% chance that the child is born with two normal genes (healthy)
• A 50% chance that the child is born with one normal and one variant gene (carrier, without disease)
• A 25% chance that the child is born with two variant genes (at risk for the disease)

Note: These outcomes do not mean that the children will definitely be carriers or be severely affected.

Related Information

References

Jones KL, Jones MC, del Campo M. Genetics, genetic counseling, and prevention. In: Jones KL, Jones MC, del Campo M, eds. Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 2.

Korf BR, Limdi NA. Principles of genetics. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 31.

Scott DA, Lee B. Patterns of genetic transmission. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 97.

Sondheimer N. Patterns of single-gene inheritance. In: Cohn RD, Scherer SW, Hamosh A, eds. Thompson & Thompson Genetics and Genomics in Medicine. 9th ed. Philadelphia, PA: Elsevier; 2024:chap 7.

Yilmaz F, Beck CR, Lee C. The chromosomal and genomic basis of disease: Disorders of the autosomes and sex chromosomes. In: Cohn RD, Scherer SW, Hamosh A, eds. Thompson & Thompson Genetics and Genomics in Medicine. 9th ed. Philadelphia, PA: Elsevier; 2024:chap 6.

Review Date: 1/26/2026  

Reviewed By: Anna C. Edens Hurst, MD, MS, Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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