difficult to set seed on this species with N. tabacum pollen, even 
with hand pollination. Usually any seed set fails to germinate; 
when it does, the hybrids are sterile (17). Thus perpetuation of 
the genetic alteration by transfer of pollen outside the 
experimental plot is extremely unlikely. Unrelated plant species 
cannot be pollinated by tobacco pollen. 
5A 3, Excision of the Inserted Recombinant DNA from the Genetically 
Engineered Plants 
Several hundred healthy tobacco plants with ADH-T DNA (HADH2 
plants), over the past two years, have been carefully examined by 
Agracetus' scientists, consultants and technicians. There has been 
no instance of any genetically engineered plant spontaneously 
exhibiting a crown gall. Almost all of these plants have been 
observed from the seedling stage through development of mature 
seeds. Since the crown gall phenotype requires cytokinin gene 
activity, and the cytokinin gene is inactivated by the foreign DNA 
insertion, this is the result one would expect. 
If a precise excision of the gene encoding yeast alcohol 
dehydrogenase I and the bacterial aminoglycoside 
phosphotransferase gene occurs with concomitant reconstitution 
of an active cytokinin gene in the T-DNA, then the result would 
be a T-DNA that is found in a normal crown gall. If such an 
excision and ligation would occur in an HADH2 plant cell, then 
one might expect a crown gall to appear from the site of that 
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