[Phenylketonuria as a model system for DNA diagnosis of hereditary disorders]

Phenylketonuria (PKU), due to a defect in phenylalanine hydroxylase (PAH), is presented as a model system for computer-aided DNA diagnosis of genetic diseases. Eight different restriction fragment length polymorphism (RFLP) markers have been localized within the introns of the 90 kb PAH gene (located on chromosome 12). These RFLPs can be combined in 384 different ways and each combination has been defined as a particular haplotype. A special computer program has been developed to calculate the possible haplotype combinations in a PKU core family (index patient and parents), with the goal to derive unambiguously both the PAH and PKU alleles. Taking into account that participation of other members of the family (grandparents or brothers/sisters) is sometimes necessary, haplotyping by itself is sufficient to establish (or exclude) the PKU status of an individual in approximately eight out of ten PKU families.