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