Genetic engineering is a set of methods used to modify or manipulate the genetic material of an organism. Scientists may carry these processes out to enhance an organism's natural characteristics or add new characteristics. While this is often used for serious matters such as the production of proteins or research into genetic diseases, it can also be used for novelty purposes, such as creating glowing fish! Keep reading to learn more about different types of engineering, examples, and more.
What is Genetic Engineering?
Genetic Engineering is a scientific methodology that allows changing an organism's genetic material by removing, editing, or inserting individual genes. Unlike selective breeding, it permits direct manipulation of an organism's DNA to change its phenotype or characteristics.
Learn more about the principles of this methodology by checking out our article Genetic Engineering!
Bacteria and Genetic Engineering
Bacteria are a very common target of genetic engineering. This is because:
- Bacteria are easy to grow
- Bacteria reproduce very rapidly
- Can manufacture complex molecules
- Their genetic material uses the same code as all other organisms
- Their use does not carry the same level of ethical concerns as other more complex life forms
- They possess mobile genetic elements known as plasmids, which provide an easy way to insert foreign genes into a cell.
Figure 1. An electron micrograph of Escherichia coli, a bacterial species commonly used in genetic engineering.
Scientists can, and often do, genetically engineer more complex organisms than bacteria, as, especially in areas such as medical research, the simplicity of bacteria prevents the required data from being gathered. An example is the genetic engineering of rats or pigs to research human genetic conditions. As humans are a very complex organism and a mammalian (eukaryotic) organism, it would be much harder, if not impossible, to gather meaningful and representative data from bacteria that are prokaryotic unicellular organisms.
Do you know the difference between a Eukaryote and a Prokaryote? Read the article Eukaryotes and Prokaryotes to make sure!
Use of DNA Ligase and Recombinant DNA in Genetic Engineering
Genetic engineering often involves the use of recombinant DNA, also known as rDNA.
Recombinant DNA (rDNA) is DNA that is formed in a variety of ways by combining two or more fragments from two or more different sources, forming a sequence not naturally found within genomes.
One way rDNA can be produced is by using an enzyme known as DNA Ligase. This enzyme carries out a process known as ligation, the joining of two nucleic acid fragments. The full method to produce rDNA is above the level needed here, but below is a brief outline of the process of inserting a human gene into a bacterial plasmid and then using this plasmid to make bacteria produce the protein.
- The human gene is isolated from the rest of the genome, either through the use of restriction enzymes or via PCR amplification. Even if restriction enzymes are used, PCR may also be used to increase the concentration of DNA present. If PCR amplification is the first step, it is then followed by the use of restriction enzymes.
Restriction enzymes act like scissors, cutting the DNA at specific sequences, known as restriction sites, forming sections known as sticky ends. This process is known as digestion.
Sticky ends are the ends of a double-stranded DNA sequence where one strand of the double helix is left longer than the other, leaving a small section of unpaired bases. The exact sequence of these bases is determined by the restriction enzyme used.
- Cutting the plasmid with the same restriction enzyme produces complementary sticky ends to those on the cloned gene. This means that the unpaired bases on one end of the plasmid will pair with those on the gene of interest, holding the two sections of DNA together.
- The phosphate backbone of the DNA is then reformed by DNA Ligase, ligating the two sections together, forming a recombinant plasmid. (rDNA)
- This recombinant plasmid is then inserted or transformed into bacteria, which are then grown, producing the desired human protein as they express the genes found within the plasmid.
Types of Genetic Engineering
As previously mentioned, genetic engineering may involve inserting, removing, or modifying individual genes. This is one way in which genetic engineering may be categorised; however, they may also be divided based on the purpose of the genetic engineering and the methods used.
Analytical Genetic Engineering
This field uses computers to model or simulate genetic changes before producing the genetic material in real life. This is also known as in silico genetic modification, as it occurs within a computer's silicon, following the same naming conventions as in vitro and in vivo, meaning in glass and the living body, respectively.
Chemical Genetic Engineering
Chemical genetic engineering focuses on identifying, separating, and classifying different genes to provide sufficient information for their use in applied genetic engineering. This field focuses on genetic mapping, which is the location of each gene in individual chromosomes. Genetic identification develops scientists' understanding of which gene or combination of genes is responsible for what phenotypical trait.
Applied Genetic Engineering
This field puts genetic engineering to practical use, actually carrying out the manipulation of an organism's genetic material via genetic engineering techniques, modifying their phenotype to exhibit traits that we desire.
Uses of Genetic Engineering in Medicine
Genetic engineering has a huge potential to revolutionise human medical treatments. Some of the main uses of genetic engineering include:
- Gene drives
- Hybridomas
- Vaccinations
- Gene therapy
- Xenotransplantation
- Modelling genetic diseases
- Recombinant protein production
The application of genetic engineering techniques in medical research and medicine overall is vast. Some of the examples mentioned are extremely useful for us. Recombinant proteins are proteins created from the expression of recombinant DNA and can be life-saving. Hybridomas are fusions of tumour cells and a lymphocyte, used to produce monoclonal antibodies! Genetic engineering may also be used to modify pathogens' properties, allowing them to be used within vaccines.
Read our Monoclonal Antibodies and Vaccination articles to learn more about these applications of genetic engineering!
By introducing the genetic changes responsible for genetic diseases into animals, the genetic condition may be modelled, allowing for research into the condition without needing human experimental research. Xenotransplantation refers to the transplantation of animal organs into humans, and genetic engineering may be used to increase the success rate of this procedure by limiting the immune challenge foreign organs present. Gene therapy especially holds the biggest potential to revolutionise medicine and the treatment of genetic diseases via gene editing. These techniques directly alter an organism's genome to alleviate diseases with a genetic component, such as the insertion of a functioning lactase gene to alleviate lactose intolerance.
Gene drives use genetic modification to insert genes encoding a set of enzymes and a modified gene into an organism's genome. These enzymes ensure that both homologous chromosomes of an organism possess the modified gene and the enzyme's genes. This ensures that they are always passed onto offspring, and said offspring will always be homozygous for the modified gene.
Uses of Genetic Engineering in Agriculture
One of the other main areas of genetic engineering applications is agriculture. By modifying a plant, scientists may cause them to produce additional nutrients that they normally would not. They may also be modified to be resistant to chemicals, such as herbicides or pesticides, allowing these to be applied to enhance crop yields. The addition of insecticidal proteins allows plants to be naturally protected from pests. Similar modifications can also be used to convey resistance to many other pathogens such as bacteria, fungi and viruses.
Genetic engineering in agriculture can also be used to modify natural traits of plants. It can be used to modify traits of existing plant products, such as canola, or produce new compounds. They may also be modified to grow quicker, be stored for longer, and many other factors!
Figure 3. Peanut plants engineered to express Bt toxins to protect against pests.
Advantages and Disadvantages of Genetically Engineered Crops
Some of the most common genetically modified crops grown are soya, maise and rice. The use of genetically modified crops is one of the most common and widely seen examples of genetic engineering, also making it the source of most controversy about genetic modification. Below we outline some of the many advantages and disadvantages of plant GMOs (Genetically modified organisms).
Pro's | Cons |
Nutritional values may be enhanced | |
Crop yields may be increased | Modifications may affect humans in unforeseen ways |
Fewer chemicals may be needed | |
Less harmful chemicals may be used | Pests may adapt to bypass protection provided by genetic modifications. |
Food may last longer on shelves | Farmers, and therefore the food supply, become dependent on companies. |
Growth seasons may be extended | Developing countries become reliant on aid or purchases for food. |
Examples of Genetic Engineering
There are several key examples of genetic engineering applications with which you need to familiarise yourself:
- Human insulin production
- Herbicide resistance in crop plants
- Insecticidal proteins in crop plants
- New vitamin production by plants
Genetic Engineering and Human Insulin Production
Human insulin was initially extracted from animal pancreas and is now mainly produced by yeasts and bacteria. Bacteria and yeast are made to produce insulin via a process similar to that described above. The human gene was isolated, then inserted into a plasmid using DNA ligase, following sticky end creation via restriction enzymes. The plasmid was then inserted into bacteria or yeast, which are then grown in large fermenters, with the produced insulin being extracted from it.
Herbicide Resistance and Genetic Engineering
As described in the genetic engineering and agriculture section above, crop plants may be modified to possess resistance to herbicidal chemicals. This allows broad-spectrum herbicides to be sprayed onto fields, removing non-modified plants and limiting competition for resources, maximising yield.
One example is the modification of plants to be resistant to glyphosate, the active ingredient of many herbicides such as Roundup. Glyphosate acts by inhibiting ESPS, an enzyme which breaks down shikimate, causing it to build up and kill the plant. By modifying a plant to express a form of ESPS which is not susceptible to glyphosate inhibition, resistance to its herbicidal effects can be conveyed.
Insect Resistance and Genetic Engineering
By inserting genes for insecticidal proteins, resistance to insect pests can be conveyed to a plant. One example is the insertion of Bt toxins into peanut plants to protect them from lesser cornstalk borer larvae. These are crystalline proteins which exhibit insecticidal action against an array of insects and nematodes.
Genetic Engineering and Plant Vitamins
Genetic engineering may be used to make crops possess vitamins that they otherwise would not. A key example of this is golden rice. This is rice modified to produce the pigment beta-carotene. This not only gives the rice its namesake golden colour but is metabolised to vitamin A within the body. Growth of this rice crop in place of regular rice aids with alleviating vitamin A deficiency in areas where rice is a staple, such as parts of Africa and South Asia.
Uses of Genetic Engineering - Key takeaways
- Genetic engineering involves changing an organism's genetic material by removing, editing or inserting individual genes.
- This is often done using recombinant DNA, or DNA comprised of two or more fragments fused to create a section of genetic material not seen in nature.
- Genetic engineering allows the modification of an organisms phenotype to that desired by scientists with applications in medicine and agriculture.
- Some key uses include the production of human insulin by bacteria and the modification of plants to become resistant to insect pests and or herbicides, along with their modification to produce additional nutrients.
References
- Figure 1: E Coli (https://www.flickr.com/photos/54591706@N02/7316101966) by NIAID (https://www.flickr.com/photos/niaid/). Licensed by CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/).
- Figure 3: BT Toxin Peanut (https://commons.wikimedia.org/wiki/File:Bt_plants.png) by Herb Pilcher, USDA ARS. Public Domain.
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