Genetically modified crop
Genetically modified crops, also known as GMO crops have had a bad reputation due to the skepticism of their effects on humans and the ecosystem. however, they can be very helpful. Scientists were first introduced to the selective breeding and modification of plants by Gregor Mendel, a monk, whose studies showed that desirable traits can be bred into the plants. Through the years, many methods have been developed to genetically engineer plants making them resistant to pests and disease. GM plants may even contain more nutrients.
Several techniques exist to create genetically modified plants. One of these is through a method called the gene silencing. In this technique, bio-technologists remove a gene that produces an undesirable trait. First, the gene is identified and removed. Then they attach a copy of the same gene, but in the opposite direction which stops the plant from expressing the characteristic. Viruses can also be used to insert DNA for a certain trait. The virus is first transformed with recombinant DNA, which then serves as a vector (genetic carrier) and is used to infect cells with the foreign DNA. Electroporation is a method in which the cells that are to be modified are placed in a solution that has the desired DNA. Then, the solution is given a short electric shock. This allows little pores to open in the cell walls, thereby letting desired DNA to enter the cells. After this, they are put in a different solution which encourages the repair of the cell walls, trapping the new DNA in these cells.  One other technique for plant modification is the use of a gene gun. In this method, extremely small particles of tungsten or gold are covered with the fragment of transgene DNA and then shot at high velocities into the plant cells.The pellet will go through the cell and leave the DNA behind where it becomes part of the cell, thereby modifying it. Scientists also use a bacterium called Agrobacterium tumefaciens (which is found in the soil), as a vector. In nature, this bacterium transfers its DNA into plants, causing crown gall disease. Scientists have used this ability to their benefit by disarming its disease-causing properties and inserting different DNA for it to introduce into plants. This method is more controlled than the gene gun method, but does not work as well in all plant species. 
Pros and Cons
The use of genetically modified plants and crops has been the source of numerous controversies. GMO foods are known to cause serious allergies for some people. This is caused by the foreign proteins introduced into the plants. The proteins added could be from a plant that they are allergic to causing a reaction. Also, some genetically modified plants are engineered to be resistant to diseases and viruses by adding antibiotic genes to the plant so that the resistance to these diseases is built in. These antibiotics can remain in the consumer's body and actually reduce the effectiveness of antibiotics medications. This effect is being observed in hospitals around the world. Scientists also worry that these modified varieties will escape into the wild and create 'super-weeds' that will be virtually impossible to eradicate using common herbicides. Or, they may start growing in the wild and create a competition that will drive the native plants into extinction.
Although GMO crops have a bad reputation, they actually have a lot of benefits. For example, because these plants require much less fertilizer, labor, and tools, they can reduce the amount of pollution to the environment. Also, plants that have been modified to contain larger amounts of nutrients can help to fight malnutrition around the world. Plants have been engineered to contain a bacterium that is toxic to insects, but safe for humans. This is very beneficial because it reduces the amount of pesticides farmers have to use, which reduces the consumer's exposure to dangerous chemicals. Another benefit, though often overlooked, is that GMO foods can also be engineered to have better flavor. 
Commonly Modified Plants
There are many plants that are commonly subjected to genetic modifications. There are generally practical reasons that exist to justify these modifications. Soy is very well known for being genetically modified. It is estimated that around 90 percent of the soybeans produced have been modified. Most of the time the soy is modified so they will be resistant to Round Up, which is an herbicide the soy growers use to kill weeds. When the soy plants are made so they are naturally resistant to the herbicide, more herbicides can then be used to kill the weeds without fear of damaging the crops. Additional modified plants include: corn, canola oil (from rapseed oil), cotton, zucchini, sugar beets, yellow squash, and papayas.  Plants can be modified to resist herbicides (like the soy plants and the Round Up), or to be made toxic to certain pests. This technique is often used in cotton. Tomatoes, however, are modified for a slightly different purpose. They are engineered to resist the production of a certain chemical, helping them to retain their quality for a longer period of time. In the future, some plants will be genetically altered to have the ability to be turned into biofuel more easily. Plants can also be genetically changed to contain more nutrients. For example, GMO rice has been called 'golden rice' due to the high levels of vitamin A it has. 
Brief explanation regarding common myths and truths surrounding the topic of genetically modified crops.
- Murnaghan, Ian. Types of Techniques Used to Genetically Modify Food Genetically modified foods.co.uk. Web. Date of last update: 26 November 2014.
- P., Byrne. Genetically Modified (GM) Crops: Techniques and Applications Colorado University. Web. Date accessed: 26 April 2015.
- Duvauchelle, Joshua. Pros & Cons of GMO Foods Livestrong.com. Web. Date of last update: Jan 13, 2014.
- Keenan, Chris. Top 10 Most Common GMO Foods The Cornucopia Institute. Web. Date of publication: 19 June 2013.
- Murnaghan, Ian. What are the Most Common GM Foods? Genetically Modified foods.co. Web. Date of Last Update: 30 January 2015.