Genetic Engineering
Humans have been messing with genes throughout human history. We've used genetics to make better animals for consumption, to make plants more resistant to disease, and to influence the genetics of our children by selecting for specific traits in a mate. But in this section, we will talk about a different type of "messing" with genes, a process called biotechnology, or genetic engineering.
Genetic engineering refers to the field where scientists can directly manipulate the production of a protein or RNA for human products. In this section we will go over some of the methods scientists use. It is kind of like building with Legos…
First, let's talk about cloning. In the media you will probably hear about cloning more often in the terms of creating a whole animal (remember Dolly the sheep, anyone?) or the possibility of cloning a human being. Rather than talking about cloning an organism, we will talk about a type of cloning that is much less controversial and much more common: the cloning of a gene. In fact, many of the products you use on a daily basis are created with the help of this type of molecular cloning.
It is common in the field of biotechnology to isolate a gene that encodes for a particularly useful protein or RNA product. Scientists can create more of this DNA, and even modify the gene such that the protein product is better suited for a scientist's needs. But, first thing's first. Let's talk about the steps of cloning a DNA fragment.
- First the fragment containing the gene of interest must be isolated, or cut out of a mass of DNA.
- The piece of DNA must be ligated, or glued into another DNA molecule. For example, the gene can be transferred to make a circular piece of DNA called a plasmid.
- This piece of DNA is then transferred into a cell through a process called transfection.
- Scientists then select for cells that contain the cloned DNA. They can use the cells to express large amounts of the gene interest.
Many gene products are produced this way, often growing the product in bacterial cells or simple eukaryotic cells such as yeast. One of the first applications of this technology was insulin. Diabetics today get their insulin from genetically modified bacteria containing the insulin gene. Vaccines are also often produced with the help of genetic engineering.
In the laboratory, scientists commonly use genetic engineering to make genetically modified organisms. Now we know you might be thinking of Frankenstein here, but in reality these organisms are a lot less scary (but much cooler). Let's talk a little bit about the genetic engineer's bag of tricks.
Scientists often make gene knockouts, where one or more of an organisms genes is made to not function. The initial steps to making a gene knockout are pretty much the same as cloning a gene.
- The scientists make a DNA construct that is targeted to the gene locus.
- The construct can be put into a cell, specifically embryonic cells. These embryonic cells are put into an early embryo.
- The DNA is taken up by the embryo, a term called recombination, and sometimes incorporated into the germ line.
- Resulting generations can be bred that do not contain the gene of interest.
- Animals can then be studied to understand the function of the gene that was eliminated.
Other times scientists create knock-in animals. In this case, a new gene is inserted into the genome of an organism. There are all sorts of uses of gene knock-ins. One example is that a fluorescent protein can be inserted under the control of a specific promoter. Whenever the promoter orders gene expression, the knocked in gene will be expressed.
Alternatively, a fluorescent protein, or tag, can also be added on to a gene that a scientist is trying to study. The result is that the protein will fluoresce in the animal. Scientists will be able to tell exactly where a particular protein is, or if it is specially localized to specific cells or tissues. This technique has been used in fish to "light up" regions of the nervous and digestive systems. Fluorescent kittens have been used for AIDS research. In many ways, genetic engineering is only limited by the imagination of scientist.
Some human disorders can be linked to a mutation in a specific gene. Some examples are cystic fibrosis, hemophilia, and sickle cell anemia. The ability to replace a "faulty" gene with a "good" copy in humans would be a huge advantage. Gene therapy is the way that scientists attempt to do this feat. Scientists have had some success at using viruses and liposomes to introduce genes into a host's genome, although this area of research is still in early stages.
Genetic engineering also offers the opportunity for the creation of organisms that benefit humans. Our ability to understand human diseases has been extremely advanced by studying genetically engineered animals. However, the tools can also be used for other purposes.
Allerca has reportedly engineered hypoallergenic dogs and cats. According to Allerca, you can now snuggle with one of their furry felines without red eyes and itching….for about $7000 that is. The company has been somewhat controversial, but it none-the-less spotlights how genetic engineering has the potential to drastically change the way we live.
The Simpsons gene, according to the TV show, is the mutated gene that contributes to Homer's baldness and laziness. It is only present on the Y chromosome, which explains why only the men in the Simpson family have the trait. Sound like pure TV ridiculousness?
Scientists have found that deletion of a gene in mice, called RGS14, actually makes mice smarter. Perhaps there is a Homer Simpson gene after all._CITATION_UUID_ 8314DF76114F44C1B8D364557CC1CAC1_ Can you envision the possibilities? No, we are not talking about making genetically engineered kids here. But, what if you could find a drug that targeted the same gene? Genetic engineering brings up some sticky questions and a lot of murky answers.
Getting rid of a gene should never be taken lightly. As you have learned, genes play some important functions. It is not so straightforward to get rid of a gene and have everything be okay. Sometimes getting rid of a gene can have some severe consequences, even resulting in the death of the organism. Therefore, scientists need to be ethical and responsible. Don't believe us? Watch I Am Legend. In the movie genetic engineering results in the production of a virus that is supposed to cure cancer. Instead the virus mutates and spreads throughout the world, killing most of the world's population. Of course, things are often a bit more dramatic in Hollywood….