The cells contain an effector gene under control of a transcriptional control element that causes {HEAD ~ the gene} to be expressed in {TAIL ~ relatively undifferentiated cells} in the population 
to be expressed in
The cells contain an effector gene under control of a transcriptional control element that causes { HEAD ~ the gene } to be expressed in { TAIL ~ relatively undifferentiated cells } in the population
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH