Human Gene Therapy 
individual involved, since the effects go beyond that individual. If 
and when germ line therapy is approved by society for clinical trials, 
then the decision to apply it in any individual case again should be 
made privately by the patient with his/her doctor. 
In conclusion, my position is that germ line therapy, since it is the 
correction of a genetic defect (albeit in the future), would be ethical 
and appropriate if the three conditions discussed above were met. 
ENHANCEMENT GENETIC ENGINEERING 
The third level of genetic engineering, enhancement genetic engineer- 
ing, is considerably different in principle from the first two. This is 
no longer therapy of a genetic disorder; it is the insertion of an addi- 
tional normal gene (or a gene modified in a specific way) to produce 
a change in some characteristic that the individual wants. Enhance- 
ment would involve the insertion of a single gene, or a small number 
of genes, that code for a product (or products) that would produce 
the desired effect — for example, greater size through the insertion 
of an additional growth hormone gene into the cells of an infant. 
Enhancement genetic engineering presents a major additional scien- 
tific hurdle, as well as serious new ethical issues. Except under very 
specific circumstances as detailed below, genetic engineering should 
not be used for enhancement purposes. 
Scientific and llthical Concerns 
The scientific hurdle to be overcome is a formidable one. Until now, 
we have considered the correction of a defect, of a ‘broken part’, if 
you will. Fix the broken part and the human machine should operate 
correctly again. Replacing a faulty part is different from trying to 
add something new to a normally functioning system. To insert a 
gene in the hope of improving or selectively altering a characteristic 
might endanger the overall metabolic balance of the individual cells 
as well as of the entire body. Medicine is a very inexact science. 
Every year new hormones, new regulators, and new pathways are 
discovered. There are clearly many more to be discovered. Most 
impressive is the enormously intricate way that each cell coordinates 
within itself all of its thousands of pathways. Likewise, the body as 
a whole carefully monitors and balances a multitude of physiological 
systems. Much additional research will be required to elucidate the 
effects of altering one or more major pathways in a cell. To correct 
a faulty gene is probably not going to be dangerous, but intentionally 
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