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1 produce viable, healthy hybrids, which can be propagated 
2 in tissue culture. 
3 It is interesting that some would argue that 
4 there is a biological risk associated with this process, 
5 which is unrelated to recombinant DNA techniques. But 
6 I would like to point out that these kinds of experiments 
7 have been going on in hundreds of laboratories since the 
8 early 1960 's without any indication of risk. 
9 In such hybrid cell populations, one can trace 
10 the loss of human chromosomes and correlate that loss with 
11 particular human traits. In this way it has been possible 
12 to use hybrid cells to map human genes to particular human 
13 chromosomes. Since 1970 , more than 200 genes have been 
14 mapped in man using this technique in a number of labor- 
15 atories. The basic knowledge gained has contributed to 
15 our understanding of primate evolution, the mode or action 
17 of gene mutations which result in specific genetic 
10 abnormalities in man. And to cite a specific case, these 
19 studies have resulted in a better understanding of the 
2Q genetic control of the interferon system, which is 
21 instrumental in protecting organisms, including man, 
22 from viral infection, and which shows promise as an 
23 anticancer therapeutic agent. 
24 Also, a great deal of information has been 
25 provided on many other interesting and important biological 
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