‘Autosomal’ means the mutation is in a gene on the non-sex chromosomes, so children of either sex can inherit the condition. ‘Recessive’ means both copies of that gene have to be mutated for someone to have the condition. If only one copy of the gene is mutated, that person is a carrier and will have no symptoms.
If mother and father are both carriers, (see first diagram), there is a:
- 25 percent chance that each child will be unaffected
- 50 percent chance that each child will be a carrier
- 25 percent chance that each child will have the condition.
Parents with autosomal recessive conditions will pass on one copy of the mutated gene to their children (see second diagram). It is very unlikely their children will be affected (unless the other parent is a blood relative).