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