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