{HEAD ~ The method} used to introduce {TAIL ~ these genes} could be methods described in the art such as electroporation, lipofectine, lipofectamine or other 
{ HEAD ~ The method } used to introduce { TAIL ~ these genes } could be methods described in the art such as electroporation , lipofectine , lipofectamine or other
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH