tokens: This hybrid clone , designated NR2 , was characterized by several methods , including PCR , with eight pairs of oligonucleotides mapped to Chr 20 : D20S5 , D20S41 , D20S42 , D20S56 , D20S57 , D20S58 , adenosine deaminase ( ADA ) , and Prion protein ( PRIP ) ; Restriction Fragment Length Polymorphism ( RFLP ) analyses with four genomic anonymous probes ( D20S5 , cD3H12 , D20S17 , D20S18 ) ; and fluorescent in situ hybridization ( FISH ) with total human DNA and D20Z1 , a sequence specific to the human Chr 20 centromere , as probes .