About Dominant Disorders
Autosomal dominant inheritance occurs when an alteration in just one copy of an inherited gene pair causes a genetic disorder.
Each parent passes one copy of every gene to a child. If one parent carries a mutation/variant, the child has a 50% chance of inheriting the abnormal copy of the gene and a 50% chance of inheriting the normal copy.
The same risk applies to each conception, regardless of the outcome of previous conceptions.
Sometimes a dominant disorder appears in an individual whose parents do not have the disorder. This situation occurs when either:
- A new mutation/variant in a dominant gene causes a disorder to appear for the first time in a family.
- The disorder has ‘reduced penetrance’, meaning that only a percentage of individuals who have the mutated/variant gene will develop the disorder, with DYT1 Generalised Dystonia being an example.
Dominant disorders can occur across multiple generations of a family and multiple family members can be affected in one generation. Except when there has been a new mutation/variant, every affected individual has a parent who carries the mutation/variant.