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Here, we show that the Duffy antigen/chemokine receptor gene ( DARC ) is composed of a single exon and that most Duffy-negative blacks carry a silent FY*B allele with a single T to C substitution at nucleotide -46 .
 ( DNA: Duffy antigen/chemokine receptor gene, None) , ( DNA: exon, None) , ( protein: Duffy antigen/chemokine receptor, None) , ( DNA: DARC, None) , ( DNA: silent FY*B allele, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( DNA: Duffy antigen/chemokine receptor gene, None) , ( DNA: exon, None) , ( protein: Duffy antigen/chemokine receptor, None) , ( DNA: DARC, None) , ( DNA: silent FY*B allele, None) 