Biology 12-2.1c Recombinant DNA
How rDNA Is Used in Biotechnology
All life forms—both extinct and living—store their genetic material in DNA molecules. The potential uses of biotechnology in our everyday lives are limited only by our imaginations. Would you want to clone your favourite pet? Would you change your eye, hair, or skin colour? Does the world need square corn on the cob so that butter doesn't drip off it? Should your life span be 200 years or more? Today, rDNA technology seems to raise more questions than answers because the potential applications are almost endless. Biotechnology is both a science and an industry. It manipulates naturally-occurring processes to meet a growing wish list of human needs and desires. Transgenic organisms—those with foreign DNA added to their own—include bacteria, plants, and animals. You'll recall that a major function of DNA is to code for proteins. Therefore, recombinant DNA codes for altered versions of those proteins. Read the following examples of current applications of rDNA in agriculture and pharmaceuticals. Keep in mind that there are many more applications of rDNA technology in medicine, industry, environmental science, and other fields of study! Pharmaceuticals: Insulin Production Our bodies normally produce insulin in response to increased blood glucose levels. Type 1 diabetes results when the pancreas does not produce insulin. Individuals affected by this type of diabetes require treatment that includes insulin injections. Before rDNA, cow and pig insulin was given to diabetic patients. However, some patients' immune systems reacted against it, because it is not identical to human insulin. Now, rDNA technology is used to mass produce human insulin by using the bacteria E. coli-a bacterium found in, among other habitats, the human intestinal tract. The insulin gene is injected into an E. coli vector, where it combines with bacterial plasmid DNA. The insulin produced by rapidly reproducing E. coli is identical to what our bodies normally produce. Similarly, rDNA technology is used to make parathyroid hormone, blood proteins for the treatment of anemia and hemophilia, and human growth hormones. By using rDNA to add foreign genes to plant genomes, plant crops can be improved in a number of ways. For example, genetically engineered bacteria can be sprayed on strawberries to protect them from freezing. Other agricultural uses of rDNA include delayed ripening, increased crop yields (the potential to grow more food on less land), and resistances for herbicide, insect, fungus, and disease.
what is recombinant dna?
By knowing the structure and replication process of DNA, scientists are able to manipulate the genetic material of an ever-increasing number and variety of organisms. Genetic engineering is defined in your textbook as "the alteration of genomes for medical or industrial purposes." Recombinant DNA (rDNA) is said to be "genetically modified." Creating rDNA is therefore one example of genetic engineering.
At which stage in production of rDNA does cloning occur?
Gene cloning occurs when the plasmid, which now contains its own DNA and foreign DNA from another species, re-enters the host cell and begins to replicate as the host divides.
How Recombinant DNA Technology Works
Genetic engineering is a term synonymous with recombinant DNA technology, and producing rDNA is one way for scientists to clone DNA. But how, exactly, can the DNA from one organism be added to that of another? To create rDNA, several steps are required. First, DNA is removed from cells of two different organisms, for example, human and bacterial DNA. The bacterium provides a vector—a piece of host organism DNA to which foreign DNA can be added. Bacteria are often used as vectors because they have DNA in plasmids as well as in their chromosomes, making them easier to work with. Restriction enzymes cut DNA in specific locations, and DNA ligase pastes human DNA to the gap in the plasmid. This creates recombinant DNA, but it is only useful if it can be mass-produced as the host cell multiplies.
Name and describe the functions of two enzymes required to produce rDNA.
Restriction enzymes: used to cut DNA strands in certain locations, creating gaps into which foreign DNA can be inserted. DNA ligase: seals foreign DNA into the opening created by restriction enymes.
Define Recombinant DNA:
a mixture of DNA from two or more different organisms; segments of DNA from one organism are inserted into the chromosomes of another host organism
recombinant DNA
a mixture of DNA from two or more different organisms; segments of DNA from one organism are inserted into the chromosomes of another host organism
vector
a piece of a host organism's DNA to which another organism's DNA can be added
genetic engineering
changing an organism's DNA to serve medical or industrial purposes
plasmid
rings of bacterial DNA to which foreign DNA is added