Inheriting a disease, condition, or trait depends on the type of chromosome affected (autosomal or sex chromosome). It also depends on whether the trait is dominant or recessive.
A single, abnormal gene on one of the first 22 nonsex chromosomes from either parent can cause an autosomal disorder.
Dominant inheritance means an abnormal gene from one parent can cause disease, even though the matching gene from the other parent is normal. The abnormal gene dominates.
Each child’s risk is independent of whether their sibling has the disorder or not. For example, if the first child has the disorder, the next child has the same 50% risk of inheriting the disorder. Children who do not inherit the abnormal gene will not develop or pass on the disease.
If someone has an abnormal gene that is inherited in an autosomal dominant manner, then the parents should also be tested for the abnormal gene.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.