99 
I simply don't know. I think there are somewhat different considerations 
in the virus field, and perhaps Dr. Melnick would like to comment on those. 
DR. FREDRICKSON: Dr. Melnick? 
DR. MELNICK: As I have listened to the sessions today, there is a 
big gap in knowledge as to whether the recombinant DNA is expressing itself 
in E. coli. The only experiments that I heard about this morning were the 
ones that Dr. Hogness did, where he put Drosophila DNA into .E. coli . I 
wonder if he could tell us a little bit about the expression of that DNA. 
DR. HOGNESS: There is one experiment in which you look at random in- 
serts of DNA into plasmids in the following way. There are bacteria which 
generate mini-cells which don't contain the I£. coli chromosome, but they 
do contain the plasmids. So you can ask what proteins are made from the 
genes in the plasmid without being bothered with all the background that 
is generated by the chromosome of the E^. coli . 
When 50 hybrid plasmids were looked at in this way, five new proteins 
were detected which could have come from the inserted Drosophila DNA. 
Since each hybrid contains 10,000 base pairs on the average, a total of 
500,000 base pairs was looked at. Hence, we detected only one new protein 
per 100,000 base pairs of Drosophila DNA. This is a maximum estimate. 
DR. MELNICK: Are those proteins Drosophila ? 
DR. HOGNESS: We don't even know that those five were coded by Droso- 
phila sequences. They could have been. By comparison, when the same ex- 
periment was done with inserted DNA from a prokaryote, IS. subtilus , an 
average of one new protein per 1,000 base pairs of _B. subtilus DNA was 
detected. Hence, we conclude that expression from prokaryotic DNA is much 
more likely in E^_ coli K12 than expression from eukaryotic DNA, such as 
Drosophila . 
DR. MELNICK: Are those proteins the same type that are expressed in 
Drosophila ? 
DR. HOGNESS: We don't know about that. All we know is that they are 
made due to the inserted Drosophila DNA. They could be due to a coding 
sequence within the parent plasmid, or to some disruption of the control 
mechanism. There are a lot of outside guesses for the mechanism by which 
these new proteins might have been produced. 
There are similar experiments done with yeast by John Carbon, where 
you ask for a natural transformation of _E. coli function, and then ask how 
frequent that is compared to the same thing when you are transforming with 
coli to coli. There again, the frequency is reduced for the eukaryote, 
yeast. 
[ 240 ] 
