The blood of a two week-old infant is collected for a Phenylketonuria, or PKU, screening Dec. 12 at Eielson Air Force Base, Alaska. PJU is a recessive genetic disorder that can cause problems with brain development, which could lead to mental retardation and seizures. All infants born at Eielson are screened for PKU at their two week well baby check up appointment. (U.S Air Force photo/Staff Sgt Eric T. Sheler)