About Dominant Disorders

Jnetics does not currently screen for dominant disorders. NHS England will shortly offer screening for BRCA for anyone with at least one Jewish grandparent.

Autosomal dominant inheritance occurs when an alteration in just one copy of an inherited gene pair causes a genetic disorder.

An individual who possesses a gene for a dominant disorder usually develops the disorder and is affected by it.

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.

Autosomal Dominant Inheritance

Sometimes a dominant disorder appears in an individual whose parents do not have the disorder. This situation occurs when either:

  1. A new mutation/variant in a dominant gene causes a disorder to appear for the first time in a family.
  2. 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.