UNIVERSITY OF CALIFORNIA, LOS ANGELES 
BERKELEY • DAVIS • IRVINE • LOS ANCELES ■ RIVERSIDE • SANDIECO • SAN FRANCISCO 
SANTA BARBARA • SANTA CRUZ 
DEPARTMENT OF PEDIATRICS 
October 22, 1984 
UCLA SCHOOL OF MEDICINE 
HARBOR-UCLA MEDICAL CENTER 
1000 WEST CARSON STREET 
TORRANCE, CALIFORNIA 90509 
Dr. William J. Gartland 
Executive Secretary, RAC 
National Institute of Allergy 
and Infectious Diseases 
Building 31, 3B-10 
Bethesda, MD 20205 
Dear Dr. Gartland: 
We write in response to a communication from Mr. Jeremy Rif kin to the RAC 
requesting that all transgenic experiments between species be terminated 
in order to protect species purity. Our letter restricts itself to the im- 
pact of this request on human genetic experimentation and potential therapy. 
We shall not address ourselves to the propositions of species integrity, 
since as we shall point out below, this issue has no practical relevance to 
human genetic investigations. 
Transgenic experiments between species are especially important to the ad- 
vancement of human genetic knowledge — basic and applied. Our direct un- 
derstanding of mechanisms of gene function and regulation depends on the 
isolation, modification, and functional evaluation of cloned genes. This 
kind of experiment can be best accomplished by the transfer of human genes 
into laboratory mice. The transfer of human genes into human embryos for 
experimental purposes is obviated on account of moral, ethical, and prac- 
tical considerations. The mouse provides an acceptable alternative, pro- 
viding as it does, a means of evaluating genetic expression in all cell 
types at all stages of development in a reproducible manner. The transfer 
of human genes into laboratory mice cannot be considered as modifying the 
genetics of the murine species, since only laboratory mice will be used, 
and these animals will either be confined to the laboratory or killed at 
the end of an experiment. 
In addition to obtaining basic information on the functioning of human 
genes, transgenic experiments will provide the most effective way of test- 
ing modified human genes for the purpose of somatic cell genetic therapy. 
Many laboratories are currently attempting to ameliorate certain human 
genetic diseases by means of the transfer of human genes into the body 
cells of patients. It is generally believed that serious genetic diseases 
such as sickle cell disease, and various thalassemias can be treated in this 
way. The prohibition of interspecific transgenic experiments would likely 
slow down or abort the development of these new therapies. 
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