jem49

If one parent has pku, will her children be definite carriers of the disease.

[Lisa Kessler, MS, CGC]

PKU is an autosomal recessive condition.  If two people who are carriers for PKU have children together, there is a 25% chance to have a child affected with PKU and a 50% chance to have a child who is a carrier of PKU.  

Yes, if one parent has PKU (not a carrier, but is affected by the condition), all of her children will be at least carriers of the condition.  The chance that the children could have PKU would depend on whether or not the father is a carrier of PKU.  

As you may know, PKU is a metabolic condition in which individuals have none or very small amount of phenylalanine hydroxylase activity.  People with PKU cannot tolerate eating the essential amnio acid called phenylalanine and need to follow a particular diet.  If the diet is not restricted from phenylalanine, most children with PKU develop severe mental retardation.