RFLP-discordance within the human phenylalanine hydroxylase locus

A search for crossover events was performed in seven families with two phenylketonuria-affected children applying seven enzymes for the detection of eight restriction fragment length polymorphisms (RFLPs) by hybridisation with a human phenylalanine hydroxylase (PAH) cDNA probe. A discordance was detected within the PvuIIb-RFLP pattern of two affected sibs. This observation is most likely the result of a cross-over event in the PAH locus. Alternative explanations are discussed. Non-paternity could be excluded by DNA fingerprinting using the oligonucleotide probe (GTG)5.