A recessive disorder occurs when a person has a change, or disease-causing variant, in both copies of the gene associated with the condition. To have changes in both copies of the gene, one must be inherited from the egg and one from the sperm.
Someone with a disease-causing variant in one copy of a recessive gene is known as a carrier. Carriers are typically healthy and do not have the genetic condition. However, two partners who are carriers for the same recessive disorder are at risk for having a child with the condition. In each pregnancy, a carrier couple has a 25% chance of having a child with the condition, a 50% chance of having a child who is a carrier, and a 25% of having a child who is neither affected or a carrier.
Because both parents must carry the condition for there to be risk to a child, recessive conditions can hide in families for generations. Carrier screening prior to or early on in pregnancy can help you learn what genetic changes you carry.
