Carrier Test for Autosomal Recessive Conditions

Diagram of recessive gene transmission from parents to child.

Autosomal recessive conditions are genetic diseases that are passed to a child through both parents' chromosomes. Autosomal recessive diseases include Tay-Sachs disease, cystic fibrosis, sickle cell disease, autosomal recessive polycystic kidney disease (ARPKD), and phenylketonuria (PKU).

Each person inherits 23 chromosomes from each parent and so has 23 pairs of chromosomes. Each chromosome contains genes. One or both of the genes in a pair can carry a mutation and fail to function properly. In an autosomal recessive condition, both chromosomes in a pair must have a mutation for the person to have the disease. If only one gene carries a mutation, the person is a carrier of the condition but does not have any symptoms.

Carrier test information for autosomal recessive conditions
One parent is a carrier	Both parents are carriers
If only one parent carries a mutation, there is: A 50% chance in each pregnancy that their child will receive the mutation and be a carrier. A 50% chance in each pregnancy that their child will not receive the mutation and will not be a carrier or have the condition. Almost no chance that their child will have the condition.	If both parents carry a mutation, there is: A 25% chance in each pregnancy that their child will inherit the mutation from each parent (two genes) and have the condition. A 50% chance in each pregnancy that their child will receive one mutated gene and be a carrier. A 25% chance in each pregnancy that their child will not receive the mutated gene and will not be a carrier or have the condition.

Current as of: April 4, 2023

Author: Healthwise Staff
Medical Review:
Kathleen Romito MD - Family Medicine
Martin J. Gabica MD - Family Medicine
Adam Husney MD - Family Medicine
Siobhan M. Dolan MD, MPH - Reproductive Genetics