3416
To define the molecular basis of PKU , we characterized twelve restriction fragment - length polymorphism ( RFLP ) haplotypes of the PAH locus in the northern European population and observed that 90 % of the PKU alleles in this population are confined to four common RFLP haplotypes .
 PKU, PKU
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease 
Text: {0} 
Answer:
 PKU, PKU