An autosomal recessive condition, such as cystic fibrosis, occurs when both the maternal and paternal copies of a gene have a disease-causing variant (or change). Typically, each parent of an affected person has one copy of a gene that works properly and one copy that does not. The parents are unaffected and are called carriers of the disease. When both parents are carriers for the same genetic condition, their children have
- A 2 in 4 (50%) chance of inheriting one disease-causing variant. In this case, the child would be a carrier, like the parents
- A 1 in 4 (25%) chance of inheriting both disease-causing variants and being affected by the genetic condition
- A 1 in 4 (25%) chance of inheriting neither disease-causing variant. In this case, the child will not be affected by the condition nor a carrier of it