rDNA Method
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At the heart of genetic engineering lies the technique of recombinant DNA. The Oxford American Desk and Thesaurus states that recombinant means, "formed by recombination." Simply put, recombinant means that a portion of something is taken and recombined into another entity. This is what we mean by recombinant DNA. Recombinant DNA essentially means that parts of a strand of DNA is cut out and connected onto another strand. Since the early 1970's scientists used this method to do genetic engineering. This section of the site will explain how this process is done and how genetically engineered DNA is made in labs all over the world. However, to understand much which is said in this page, please go to the Basic Biology page, if you haven't already done so.
Restriction enzymes make genetic engineering possible. An enzyme is a protein which serve as catalysts for many biochemical processes. Restriction enzymes "read" the DNA parts and cuts it at the base sequence. These enzymes recognize the sequences as specific points of the DNA and then severing the molecules at that point. Doing this will cause the DNA to break and have "sticky ends." They are called sticky ends because the end which is "sticky" perfectly fits with another end and it seems like they are sticking to each other. By using these sticky ends, scientists can connect the cut segment of the DNA onto a plasmid.
Plasmids are circular strands of DNA which are often used for gene splicing. Plasmids are found in bacterium and scientists use them to insert the desired trait into another organism. Plasmids are also cut using restriction enzymes and then the foreign trait is connected where it is cut. For the "sticky ends" to stick, special linker sequences, also enzymes called DNA ligase, must be put onto the segment of DNA. Then, the segment will connect and fill the gap left in the plasmid. Since DNA for all living things are identical, this process will work on anything. By doing this, many things which nature did not intend for something to do can be done. For example, food can grow exponentially in size, taste, and nutrition.
When the combining of the DNA is over, only one new DNA is completed. Of course, doing this process to each and every plasmid is not realistic with today's technology. So how do scientists make the plasmids reproduce? They take the altered plasmid and put it into a bacterium, usually E. coli. When they do this, the bacteria cell will follow the plasmid's instructions and produce the amino acids it tells them to, which causes the desired trait, and also lets the bacterium transfer this information when it reproduces, causing many of them to make the trait. To isolate only the bacteria that take the modification, scientists can insert a gene that makes the bacterium immune from a particular antibiotic along with the desired change, and then treat the population with the antibiotic, leaving only those bacteria that have been genetically engineered.
By using recombinant DNA methods, the science of genetic engineering can work. Scientists can use this procedure to create many new things like in agriculture and medicine. Recombinant DNA technology speeds up the process of evolution and selective breeding by many, many generations. This technology has the power to make much of today's society's problems go away, like the lack of food, and the incurability of certain diseases. However, just like nuclear power, it can also do many bad things. Whether this technology is used for good or bad purposes, people from both sides of the argument about the pros and cons of rDNA can reach a consensus that this will undoubtedly impact the near future. To learn more about the vast uses of genetic engineering, click here.
Sources
- “Activity 6: Recombinant DNA Techniques.” Access Excellence. 18 Aug. 2004. <http://www.accessexcellence.org/RC/AB/WYW/wkbooks/SFTS/activity6.html>.
- Jefferis, David. BioTech. N.p.: Crabtree Publishing Company, 2002.
- Oleksy, Walter. Miracles of Genetics. Chicago: Children’s Press, 1986.
- Rantala, M.L., and Arthur J. Milgram, Ph. D. Cloning: For and Against. N.p.: Carus Publishing Company, 1999.
- “Recombinant DNA Technology .” New Mexico State University. 18 Aug. 2004. <http://darwin.nmsu.edu/~molbio/mcb520/lecture2.html>.
- “Recombination Up Close.” Access Excellence. 18 Aug. 2004. <http://www.accessexcellence.org/RC/AB/BC/Recombination_Up_Close.html>.
- Reiss, Michael J, and Roger Straughan. Improving Nature? N.p.: Cambridge University Press, 1996.
- “Speaking the Language of Recombinant DNA.” Access Excellence. 18 Aug. 2004. <http://www.accessexcellence.org/RC/AB/IE/Speaking_Language_rDNA.html>
Image Sources
- http://www.swbic.org/products/clipart/clipart.php