35 
Slide 1 
2S 

'Foreign' DNA 
'endonuclease 
cleavage 
° o 
o o 
o 
endonuclease 
cleavage 
Host Cell 
At the upper right of the slide is another cell, shown here as a rec- 
tangle. This cell will serve as the source of the DNA to be joined to the 
vector. The DNA is termed the foreign DNA, and it too can be cleaved by 
restriction endonucleases. The rectangular cell can represent a cell from 
any living species, and as shown here the foreign DNA might contain chromo- 
somal DNA or independent genetic elements, or both. 
The foreign DNA fragments are, in the next step, joined to the vector 
by procedures that were outlined by Dr. Berg, and the recombinant DNA is 
then reinserted into a host cell. Again, the host cell will most likely 
be of the same species as used for the isolation of the vector. 
The cells are then placed under conditions where they grow and multiply 
by division, and the resident recombinant DNA will be duplicated along with 
the chromosomal DNA, and each new cell will contain recombinant DNA. 
Now, in the experiments discussed in the guidelines, the host cells 
are generally single living cells, either microorganisms such as bacteria, 
or animal or plant cells which were originally obtained from living tissue, 
but are grown as single cells under special laboratory conditions. 
May I have the lights please, and not the next slide yet. 
The proposed guidelines start with a statement of general principles, 
and these are consistent with the general conclusions that were published 
in the report of the international conference at Asilomar, and were reviewed 
[176] 
