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