September 2, 1985
Recombinant DNA: It's Safe, But Why ?
If you were to take an opinion poll on the question "Is recombinant DNA research safe ?" many peple would say yes and they would be correct, but if you asked them the mechanisms by which it is saf they could not answer correctly if their lives depended on it. Why should anybody know how it is sfe? Personally, though, I am of the opinion that an informed public is a more alert and agressive pblic. People should be aware of the most explossive science in this decade. More advances will be ade in this field than any other except, most likely, computers. That is what I would like to discus, recombinant DNA research. After presenting some background on DNA in general I will use the bactrium(pl. Bacteria), E. Coli, to show how this research is safe.
Deoxyribonucleic acid, DNA, is the prime material of life. It governs how tall we are, our hairand eye color and just about every other physical aspect of the body. DNA is composed of four componds: adenine, A, thymine, T, guanine, G, and cytosine, C. Think of these substances as the rungs ofa ladder. Now, if you twist the ladder you have one of the most famous shapes in science, the doubl helix. In the rungs of the ladder adenine can only bond to thymine and guanine can only bond to cyosine. This may seem to restrict the variation, but if you consider that there is no limit in the nmber of rungs in the ladder then the possible variations become infinitely variable. It allows ther to be strands of DNA a kilometer long. These strands of DNA for genes which turn agglomerate to fom chromosomes in humans. In bacteria the genes do not form chromosomes. Instead they each form an ndividual loop and float around in the cytoplasm of the bacterium.
The diagram below is of a sequence of a DNA strand. The DNA sequence is not in its twisted or hlix form because it is extremely complicated looking.
Sugar---->| | |S|
NOw that you have a background on DNA in general I can talk about the mechanisms of recombinant NA. It is essentail that one know the role of the bacteroum E. Coli. in our society. The bacteriumis found in the large intestine of many higher animals. It facilitates the breakdown of fats, fattyacids and proteins so that they can be absorbed into the bloodstream. It is also responsible for th production of vitamin K, without which there is no other source @`d we would eventually die. If soe disease killed the bacterium or if a muntant form recombinant DNA, that did not make vitamin K, wee to get into our systems and take over we would die within the month.
Before scientists could start working on recombinant DNA they had to make sure that workers werenot exposed and that the bacteria could not get out of the lab, and that if it did get out of the la that it should not be able to survive. The first condition was met with the construction of new tyes of labs. First, anybody entering the research labs had to wear sterilized clothing and had to gothrough a sterilization chamber in which any stray foreign bacteria on the person's body would be kiled. All work in the labs had to be done in atmospherically controlled compartments so that if the acteria got out they would not be in a compatible atmosphere and thus, would die. No live or dead bcteria were to be poured down the sink for the fear of rapid growth of a potentially disease-causingstrain of bacteria. When researchers left the lab they would enter aother sterilization chamber andtheir clothes would be incinerated. All bacteria in the lab were to be put in enzyme solution whichbreaks down their protective protein coats. The second condition, if the bacteria got out of the la, was a little harder to deal with than the first and involved a lot more thought on the part of man famous genetics of the 1970's. In 1975, one of the most important meetings of science took place, he Asilomar conference. After going over twenty possibilities they narrowed it to one. This was toremove the DNA sequence which coded for the bacterium's protective protein coat. This coat protect the bacterium form the envirement and without it the bacterium dies. This means that if after the acterium has been altered and it gets out of the lab it can not live. This method has been in use fr the last nine years.
Now that the bacterium has been rendered harmless the scientists can proceed. First, a restricton enzyme is used to break the plasmid loop. A restriction enzyme breaks DNA at a specific point. or instance, if the enzyme will break the DNA every time it comes to the sequence ACG then the scienists can take out a very specific area. So the enzyme breaks the loop and the new sequence made by he scientists is put in. This new sequence takes about six months to create, depending on the lengt of the sequence. This new sequence is spliced into the loop using an enzyme called DNA repairase wich does just that, repair the breaks, but is at the same time introducing a new sequence which the acterium will believe is its own. After all of this the plasmid with its new sequence is put into adifferent bacterium called a host cell. The host cell will believe that the new plasmid is one of is own and will carry out all of the processes that the plasmid codes for. An excellent example of tis which is being researched right now is the aility of a bacterium to produce insulin. By injetingthese bacteria into the bloodstream of people with diabetes the disease can be controlled to a greatr degree and the person would not need daily injections of insulin to survive. This process could b rivised, perefected and available within the decade.
The field of genetics is not isolated. It is affected by advances in other fields as well. Forexample, four years ago a DNA sequence which took six months to make now only takes three weeks by icorporating the aid of a computer. Still, though, genetics is in its infancy and its future is brigt. People need not worry about safety in the labs and the threat of biohazards, rather should look orward to a future where many diseases could be abolised by genetic manipulation and recombinant DNAresearch.
1. Curtis, Helena. "Recombinant DNA", Biology. New York:Worth
Publishers, Inc., 1983.
2. Etzioni, Amitai. Genetic Fix New York:Macmillan Publishing
3. Halacy, D.S., Jr. Genetic Revolution. New York:Harper
and Row, 1978.
4. Lear, John. Recombinant DNA. New York:Crown Publishers,
5. Otto, James. "Recombinant DNA", MOdern Biology. New York:Holt,
Rinehart and Winston, Publishers, 1981.
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