For X-linked conditions, testing the mother’s DNA is sufficient to evaluate risk of having an affected child. Screening for X-linked disorders is a crucial step for patients opting for an egg donor. If the mother or egg donor is a carrier for an X-linked disease, there is a 50% chance she will pass on her mutated copy of the gene to any of her children. Females who inherit one defective copy will still possess one healthy copy from their father; these female carriers generally exhibit very mild or no symptoms of the disease. However, males who inherit a mutated copy possess no healthy copies of the gene, and will be affected with the disease.