How is mitochondrial disease inherited?
Mitochondria contain 2 types of genetic material:
- mitochondrial DNA, which can only be passed on from the mother
- nuclear DNA, which is passed on from both parents
In the following sections are listed the ways that Mitochondrial disease can be inherited:
A mother with a mitochondrial DNA gene mutation will pass this abnormal gene to all of her children. The children will all be affected, with different degrees of severity. This is called maternal inheritance.
This does not mean that the children are going to be affected in the same way as their mother. It is not possible to predict how the children will be affected. This creates a lot of stress for those who are planning a family.
Autosomal recessive inheritance
The nuclear DNA in mitochondria is inherited from both parents (half from each parent). Mitochondrial disease can be passed on only if BOTH the mother and father are “carriers”. This means that they carry the mutated gene, but not the disease – so they don’t have any symptoms. This is called autosomal recessive inheritance.
When both parents are carriers, there is
- a 25% chance of having a child with the disease
- a 50% chance of having a child who is a carrier like the parents (has the mutation, but not the disease)
- a 25% chance of having a child that is not a carrier and does not have the disease
Autosomal dominant inheritance
If one parent has a dominant nuclear DNA gene mutation, this abnormal gene will be passed on to 50% of his or her children. If the other parent has normal nuclear DNA, the children will inherit a normal nuclear DNA gene from him or her.