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