{HEAD ~ Any extensive incorporation} of {TAIL ~ the labeled nucleotide} depends on incorporation and extension of the analog by HIV RT 
of
{ HEAD ~ Any extensive incorporation } of { TAIL ~ the labeled nucleotide } depends on incorporation and extension of the analog by HIV RT
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH