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