It would not be an exaggeration to describe genetically modified organisms as products of one of the most important capabilities humans have gained through nearly 150 years of genetic research.
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.
Humans have long known that traits are passed from parents to offspring and have put this knowledge into practice. For example, the selection of breeding stock in agriculture and in dog or horse breeding has been practiced for more than 10,000 years. Crossbreeding is another method used in plants and animals to obtain offspring with desired traits.
Even before people knew about DNA or understood the underlying mechanisms, they sought to develop organisms with desired traits.
Selective breeding and crossbreeding require the organisms whose traits are to be passed on to be able to reproduce with each other. For example, crossing two wheat varieties is straightforward and allows desired traits to be passed down through 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.
Selective breeding and crossbreeding do not guarantee that the offspring will have the desired traits; the outcome depends on probability. These natural methods may pass on unwanted traits alongside the desired ones.
During the 20th century, advances in science and technology took the introduction of desired traits into organisms to a different level. After 1946, humans gained the ability to carry out genetic engineering.
In simple terms, genetic engineering can be described as changing a characteristic of an organism by intervening in its genetic structure. Unlike natural selective breeding and crossbreeding, genetic engineering allows desired traits to be transferred 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).
A person’s genetic library, or genome, contains 46 books (chromosomes): 23 inherited from the mother and 23 from the father. Each set of 23 books covers a different range of subjects.
Imagine 23 different books covering subjects such as physics, geometry and sociology. In this analogy, one physics book comes from the father and another from the mother; the same is true of the two sociology books.
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 offspring carries both versions of the eye-color information inherited from the parents in its genetic library, and the more dominant version is reflected in its physical appearance.
Genes are the individual subjects within these books, containing detailed information about a particular topic. A human has between 20,000 and 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): The term is commonly abbreviated as GMO in the singular and GMOs in the plural.
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. Development and growth of an organism with the 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.
Different techniques are available for inserting the gene into the recipient organism’s genome. Bacteria can be induced to take up foreign DNA, for example through 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 ‘FLAVR-SAVR 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 carnation 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 applications of transgenic plants include tolerance to drought and cold, as well as their use as bioreactors for producing biopharmaceuticals, biofuels or medicines.
The leading countries in the production of transgenic plants in the world are the USA, Argentina, Brazil, Canada, India and the People’s 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.
Beyond research, genetic modification is used in animal production to improve economically important traits such as growth rate, meat quality, milk composition, disease resistance and survival. Genetic engineering has also been proposed as a means of controlling mosquitoes that transmit 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 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.
References
Alberts, B., Hopkin, K., Johnson, A. D., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2023). Essential Cell Biology (6th ed.). W. W. Norton & Company.
World Health Organization. (2014). Food, genetically modified.
U.S. Food and Drug Administration. (n.d.). Science and History of GMOs and Other Food Modification Processes.
National Human Genome Research Institute. (n.d.). Talking Glossary of Genomic and Genetic Terms.
National Academies of Sciences, Engineering, and Medicine. (2016). Genetically Engineered Crops: Experiences and Prospects. The National Academies Press.
U.S. Food and Drug Administration. (n.d.). Understanding New Plant Varieties.
Halil İbrahim Akgül
Halil Ibrahim Akgul, Ph.D., is an Assistant Professor of Food Engineering at Bayburt University, where he works in the Division of Food Sciences within the Faculty of Engineering. He received his B.Sc. in Food Engineering from Akdeniz University in 2010, followed by an M.Sc. and a Ph.D. in Food Engineering from Atatürk University in 2015 and 2020, respectively. His formally recognised academic fields are Food Sciences and Engineering, Food Technologies, Dairy and Dairy Products Technology, and Food Microbiology.
Dr. Akgul has more than fifteen years of professional, research, and academic experience in food science. Between 2011 and 2013, he worked as the food engineer responsible for operations at the Pilot Dairy and Bread Factory of Atatürk University’s Directorate of Agricultural Enterprises. This industrial experience, combined with his subsequent academic research, gave him extensive practical and scientific knowledge of milk processing, dairy production, food quality, hygiene, and product development.
His research is primarily focused on milk and dairy products, dairy microbiology, starter cultures, lactic acid bacteria, exopolysaccharides, butter technology, and the physicochemical, microbiological, sensory, and nutritional properties of foods. His studies have examined the quality and fatty-acid composition of traditional butter, aroma formation in butter produced with different starter cultures, raw-milk quality, the characterisation and antioxidant activity of bacterial exopolysaccharides, traditional dairy products such as çökelek and karın kaymağı, colostrum powder, and the use of fruit-derived ingredients in ice cream production.
His academic record includes peer-reviewed research articles published in national and international journals, including Mljekarstvo, Acta Scientiarum Technology, the Journal of Food Safety and Food Quality, the International Journal of Food Engineering, the Atatürk University Journal of Agricultural Faculty, and ATA Food Journal. Four of the research articles currently listed in his university profile were published in SCI-Expanded-indexed journals. He has also contributed to twelve national and international conference papers and presentations covering dairy products, food microbiology, butter quality, fatty-acid composition, starter cultures, exopolysaccharide-producing bacteria, colostrum, traditional foods, and functional ice-cream formulations.
Dr. Akgul has participated as a researcher or adviser in eleven completed scientific and applied research projects. These projects have addressed the modernisation of pilot dairy-processing facilities; the production and quality characteristics of colostrum powder; the physicochemical and microbiological quality of butter and raw milk; the identification of exopolysaccharide-producing lactic acid bacteria; the development and production optimisation of starter cultures for mould-ripened cheese; the standardisation of traditional dairy products; and the use of sloe berry and persimmon fibre in ice-cream production.
His teaching experience spans undergraduate, associate-degree, and graduate education. The courses he has taught include Food Chemistry, Analytical Chemistry, General Chemistry, Organic Chemistry, Fermented Dairy Products Technology, Butter Production and Processing Technology, Healthy Living and Nutrition, Organic Agriculture and Food, Popular Science, Digital Literacy, and Information Technologies. Through these courses, he combines fundamental food chemistry and engineering principles with dairy technology, nutrition, scientific literacy, and the practical communication of scientific knowledge.
He is the founder and Editor-in-Chief of Gıda ve Sağlık, a multilingual digital publication devoted to food, nutrition, health, food chemistry, food microbiology, and culinary science. Through this platform, he draws upon his academic background, teaching experience, research activity, and practical knowledge of food production to present scientifically grounded information in a detailed and accessible form for an international readership.