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