It would not be an exaggeration to say that Genetically Modified Organisms are essential “the most important ability that human beings have gained through nearly 150 years of genetic studies.”
With the studies of Gregor Mendel (1822-1884), we began to discover that the characteristic features of living things are encoded in their genes about 150 years ago.
However, mankind has known for a very long time that the character is passed down from ancestor to son and has been practicing it. For example, the use of stud in agriculture, dog or horse breeding is a method that has been used for more than 10 thousand years. Likewise, crossbreeding is another method applied in plants and animals in order to obtain a son with the desired character.
Even at times when human beings did not know either DNA or the essence of the business, they were in desired to develop a living thing with the desired character traits.
The basic principle of stud breeding and crossbreeding is that the creatures whose traits are intended to be transferred must be capable of mating with each other. For example, crossing two wheat varieties is easy and allows desired traits to be passed down the generations.
However, as in the mating of horses and donkeys, despite the birth of a “mule” with the strength of a horse and the endurance of a donkey, the mule’s sterility means that strength and robustness cannot continue for generations in a single living thing.
Or, it is not possible to transfer the horse’s strength to a cow breed by crossbreeding. Therefore, breeding and crossbreeding are valid methods as long as the parents are members of the same species.
However, stud breeding and crossbreeding methods do not guarantee that the “son” will have desirable characteristics; this is a matter of probability. Sometimes these natural ways can give the son unwanted characteristics as well as desirable ones.
The development of science and technology has carried the task of giving the desired character to living things to a different dimension as of the 20th century. After 1946, human beings had the ability to do “gene engineering”.
In simple terms, gene engineering can be explained as “changing a characteristic feature in a living thing by interfering with the gene structure of that living thing.” Contrary to natural breeding and crossing methods, gene engineering makes it possible to gain the desired character between different species.
After this introduction, it is necessary to define some concepts in order to explain the subject in detail and to prevent possible confusion of meaning.
Genetic Concepts
Genetics: It is the science that examines the characters of living things on the scale of genes and hereditary materials. Also called the science of heredity. Hereditary materials are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
DNA: It is the organic material that carries information about all the character traits of the living thing and all the functioning of the organism. The information of all the functioning and structural features of the organism is available in DNA. If we were to make an analogy; we can compare DNA to the text of a book.
The letters of DNA are called “nucleotides” and there are only 4 letters in its alphabet (Adenine, Thymine, Guanine and Cytosine). All the words of DNA have three letters. Three letters come together to form meaningful words; these words of DNA are called “codons.”
The chromosome is the book. Chromosome refers to a complete work created by adding a preface, table of contents, bibliography and cover to the text of the book (DNA).
There are 46 books (chromosomes) in a person’s genetic library (genome). He gets 23 of these books from his mother and 23 from his father. The fields of 23 books are different from each other.
For example, it can be thought of as 23 different books, one of which was written in the fields of physics, one of geometry, and one of sociology… It can be imagined that in the field of physics, a book was taken from the father, a book was taken the mother; in the field of physics, a book was taken from the mother, a book was taken from the father.
This is why it is said that “man has 23 pairs of chromosomes”. However, although the fields and subject titles of the books taken from the mother and father are the same, the content of the subjects may be different.
For example, eye color, as the most frequently cited example, is a topic in book 15 (Chromosome 15); However, the content of eye color may be different in the book taken from the mother and different in the one taken from the father.
The son also has two different inscriptions about eye color taken from the mother and father in his own library and the more dominant one reflects it in his physical structure.
Genes are separate subjects within the books; It contains all the information about a subject with all the details. A human has between 20,000-30,000 genes.
Some genes are made up of a few hundred nucleotides (letters), while others are made up of millions of nucleotides. The number of genes (subjects) contained in chromosomes (books) is different from each other.
RNA is the carbon paper used to copy DNA. RNA also has a 4-letter alphabet, but unlike DNA, it has the “letter” Uracil instead of Thymine. That’s why when copying, there is Uracil in RNA versus the letter that is Thymine in DNA (For example, the codon that is “ATA” in DNA is expressed as “AUA” in RNA).
Chromosomes are located in the nucleus at the center of each cell. For example, when a protein is to be produced in the cell, the relevant part of DNA is copied in the nucleus and RNA is formed, RNA goes to the ribosomes and transfers all the information about the production of that protein to the ribosome.
Gene: A piece of DNA that can express a character trait or an action alone is called a gene.
Genetic Modification: It is the modification of a trait or a character in an organism by altering or silencing its genes. In this context, the gene of the living thing can be changed, enhanced, silenced or a gene taken from another living thing or artificially produced can be inserted into the genome of the living thing.
Recombinant DNA Technology: It is the modification of a living thing by combining genes from different living things.
Going through the example given above, let’s consider, for example, a field plant. Like every living thing, it has books (chromosomes) that carry genetic information. Imagine that a gene (subject) not found in the chromosomes of this plant is transferred, for example, from a bacterium.
Let this bacterium be capable of producing toxins against insects. When the gene responsible for the production of this toxin is copied and added to the chromosome of the field plant, a field plant that can produce toxins against insects can emerge.
Therefore, in this example, the field crop is made resistant to insects by recombinant DNA technology.
Genetically Modified Organisms (GMOs): Recombinant DNA technology is the name given to living things whose gene structure has been changed. It is generally used as an abbreviation as GMO.
Transgenic plant: Plants whose gene structure has been modified.
Transgenic animal: Animals whose gene structure has been modified.
Transgenic microorganisms: Microorganisms whose gene structure has been modified.
How Are Genetically Modified Organisms Produced?
Producing genetically modified organisms (GMOs) is generally a 4-step process. These processes are;
1. Identification of the gene,
2. Duplication or artificial production of the gene,
3. Insertion of the gene into the cell and
4. Growth of a new creature with a new genome.
First of all, the gene responsible for the characteristic feature that is desired to be imparted to the living thing must be identified and isolated from another living thing or constructed artificially. The gene is then combined with other genetic elements, including a promoter and terminator region and a selectable marker.
In the third step, different techniques are available to insert this gene into the genome of the living thing. Bacteria can be induced to take up foreign DNA, usually by exposed heat shock or electroporation.
In animals, it is usually inserted into the animal’s cells using microinjection. The injection can be done directly into the nucleus or through the use of viral vectors.
In plants, the gene is inserted, usually using Agrobacterium-mediated recombination, biolistic or electroporation.
Since the gene in question is placed in only one cell at this stage, the organism must be reproduced from that single cell. In plants, this is accomplished through tissue culture. In animals, it is necessary to ensure that the inserted gene is present in embryonic stem cells.
In the early days of genetic modification, genetic material was randomly inserted into the host genome. However, over the last 30 years, gene targeting techniques and precise localization techniques have been developed.
Among these techniques, TALEN and CRISPR are the most widely used techniques and each has its own advantages. TALENs have higher target specificity, while CRISPR is easier to design and more efficient.
History of Genetically Modified Organisms
In the 1940s and 50s, with the discovery of the way human beings changed the gene structure of a living thing, the way for the transformation of these scientific studies into commercial products was opened.
In 1982, the FDA approved the genetically modified bacteria Escherichia coli, which can produce large amounts of insulin, to provide insulin to diabetics. Thus, GMOs entered our lives for the first time.
The first genetically modified plant (transgenic plant) was produced in 1983 using an antibiotic-resistant tobacco plant. With the introduction of virus-resistant tobacco in the early 1990s, China became the first country to commercialize a transgenic product.
In 1986, with reference to the commercialization of genetically modified organisms, the USA took the first step of legal regulations regarding genetically modified organisms. In this regard, in 1992, the FDA declared that food derived from plants from genetically modified organisms must meet the same safety standards and requirements as food derived from conventionally grown plants.
In fact, the 90s were the years when the commercialization of transgenic products exploded. In 1994, the transgenic ‘Flavor Saver tomato’ was approved by the Food and Drug Administration (FDA) for marketing in the USA. These genetically modified tomatoes matured later after being picked.
By 1996, a total of 35 approvals were granted for commercial cultivation of 8 transgenic crops with 8 different traits and one clove species in 6 countries and the EU.
In 2003, the World Health Organization (WHO) and the Food and Agriculture Organization (FAO), affiliated to the United Nations, prepared international guidelines and standards to determine the safety of GMO foods.
In 2003, an animal (GloFish) was genetically modified and commercialized for the first time.
As of 2005, about 13% of squash grown in the U.S. are squashes that have been genetically modified to make them resistant to all three viruses.
As of 2011, the USA tops the list in GM production. Currently, there are different types of genetically modified foods such as cotton, soybean, canola, potato, eggplant, strawberry, corn, tomato, lettuce, melon and carrot in the world markets, to the extent allowed by their own legal regulations.
Apart from food, there are also genetically modified products such as drugs, feed, fiber and vaccines. The first genetically modified animal approved for use as food was the AquAdvantage salmon in 2015.
In 2016, the US passed a law requiring labeling for certain genetically engineered foods and mandated that the term “bioengineered” be used on the label of GMO foods.
In 2017, apples from genetically modified organisms were offered for sale in the USA. GMO pink pineapple was introduced to US consumers in 2020.
Current Status of Genetically Modified Organisms
Bacteria are the easiest organisms to genetically engineer and are subject to genetic modification for different purposes such as research, food production, industrial protein purification (including pharmaceuticals) and agriculture.
Fungi are organisms that undergo genetic modification for almost the same purposes. Viruses play an important role as vectors to add genetic information to other organisms. Viruses generally have an important use in human gene therapy.
Genetic modification is applied to plants for scientific research, to obtain new colors in plants and to produce vaccines and improve crops. The most basic application of plant modification is to establish herbicide tolerance or insect resistance. However, as in the example of “golden rice”, genetic intervention may be involved in order to increase its nutritional value.
Other areas of application for transgenic plants are bioreactors for drought and cold resistance, biopharmaceutical, biofuel or drug production.
The leading countries in the production of transgenic plants in the world are the USA, Argentina, Brazil, Canada, India and the Republic of China. Today, the most cultivated transgenic plants are soybean, maize, cotton and rapeseed.
It is often much more difficult to genetically transform animals and the vast majority are still in the research phase. Mammals are the best model organisms for humans. Therefore, genetically modified mammals are being developed to discover and develop new treatments for major diseases in humans.
Genetic modification in animals is applied to improve economically important traits such as animal husbandry, growth rate, meat quality, milk composition, disease resistance and survival, apart from research purposes. However, genetic engineering has been proposed as a way to control mosquitoes, which are a vector for many deadly diseases.
Although human gene therapy is still relatively new, studies of gene modification in humans are being conducted to treat genetic disorders such as severe combined immunodeficiency and Leber’s congenital amaurosis.
Genetically Modified Foods
A large percentage of the Canola produced in the United States today is GMO and is mostly used to produce vegetable oil. Canola oil is the third most consumed vegetable oil in the world. Gene modification in canola is applied to provide resistance to herbicides and improve oil composition.
As of 2010, 86% of the corn crop grown in the United States and Canada and 32% of the worldwide corn crop in 2011 were GMO.
Cottonseed oil is used both at home and industrially as salad and cooking oil. Approximately 93% of the US cotton crop is GMO.
95% of the sugar beets produced in the USA are produced from genetically modified seeds. Herbicide-resistant sugar beets are approved in Australia, Canada, Colombia, the EU, Japan, Korea, Mexico, New Zealand, the Philippines, the Russian Federation, Singapore and the USA.
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