Phenylketonuria can be inherited from the father or from the mother, mainly due to the presence or absence of mutations in the gene in the parents. Phenylketonuria is an autosomal recessive disorder that can be viewed as the aa gene, and the inheritance of the child is related to whether or not the parent is a carrier and has the disease, rather than to the specific sex. 1. If both parents are carriers of the disease-causing gene, which can be expressed as the Aa gene, their children will have a one-in-four chance of inheriting the aa gene and acquiring phenylketonuria. 2. If one parent is AA and the other is Aa, the child has a one-in-two chance of acquiring Aa and becoming a carrier but not developing the disease. 3. If one parent is AA and the other parent is aa, there is a 100% chance that the child will be a carrier but will not develop the disease. 4. If one parent is Aa and the other parent is aa, the child has a 1 in 2 chance of having the disease and a 1 in 2 chance of being a carrier. 5. If both parents are sick (aa), the child is 100 percent sick. It is recommended to prepare for pregnancy under the guidance of a doctor and to have genetic counseling.