Genetically modified organisms and the history of application of technology
All living organisms, including the minutest bacteria, fungi, virus, plants, insects, animals and humans on the surface of planet earth did exist in ancient times before existing currently. Existence of living organisms has been sustained because from generation to generation, traits and characters have been transferred through inheritance.
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The ability for all organisms to inherit traits and characters is possible because they all possess the basic physical and functional unit of heredity called gene. Genes provide the instructions that make protein molecules.
These molecules give organisms their looks, how they survive in an environment and how they behave in an environment.
Basic terminologies
In order to gain understanding into the science of genes, hereditary and the ability to identify, cut and move genes, this paragraph will be devoted to explaining some basic terminologies in genetics. There are four chemicals that are the building blocks that make up a gene namely Adenine (A), Cytosine (C), Guanine (G) and Thymine (T).These are called nucleotides. A long chain of four chemicals (ACGT) in different arrangements make up a gene and a gene lies in a long strand of a larger molecule called Deoxyribonucleic acid (DNA). This DNA is an extensively long chain of the four chemicals (nucleotides), which has a double helical structure, coils up, and organises into another structure called a chromosome. A chromosome therefore, is a long strand of DNA, which contains a number of genes and these genes result in proteins, each coding for specific trait or character. It is the type of protein, which result, in our unique differences.
Considering the example of humans, we possess 23 pairs of chromosomes which translate into about 20,000 to 25,000 different genes and these genes have varied combinations of ACGT which culminate into the different characters. An example is where the combination - AAACCGGTTTTT - may result in green eyes, while AAACCGGTTTAA may have blue eyes. Here, the last 10 letters - TT - and - AA - mean the colour and the first ten letters - AAACCGGTTT - mean the eye. Further advancements in scientific research revealed the ability to identify these sequences of nucleotides and isolate them from organisms through careful experiments in the laboratory.
Genetic engineering
The application of technologies to alter the genetic constitution of an entity including the transfer of genes within and across species boundaries to produce improved or novel organism is referred to as genetic engineering. Furthermore, as genes would have been transferred from one organism to the other, the technology might also be referred to as genetic transformation and the product generated is referred to as a genetically modified organism. In the laboratory, when a gene purposely moved from an organism into another organism to improve or change that other organism, the change/improved organism is referred to as a genetically modified organism (GMO).
Products of genetic engineering have been in the system for a very long time, a typical example is insulin. Insulin, which is injected directly into our blood stream is obtained from the intestines of pigs. The gene is introduced into bacteria and several copies of the insulin is produced as the bacteria grows. Further to that, the insulin is purified from the bacteria and used as medicine. Another example of using GMO is the thyroid hormone which is derived from animals. This is currently produced by bacteria. The hepatitis B vaccine as well as the chemical Aspartame used in sugar-free foods are all derived through genetic engineering.
Genetic engineering has emerged as a novel tool for overcoming incompatibility and species barriers between crops and their wild relatives and other organisms. It deals with specificity and high precision to ensure the identification of the exact gene of interest, isolate and insert it in the precise recipient organism and be certain that the progeny with required attributes has been generated. Genetic modification allows breeders to carry out not only single gene transfer but also transfer of clusters of genes from one organism to another. For example, the technique has made it possible to engineer the whole biosynthetic pathway for Provitamin A biosynthesis in rice, making rice a source of vitamin A (Dattaet. al., 2003), which no conventional breeding method can achieve (Potrykus, 2001). Major hallmarks of the transgenic technology are that, it is relatively precise, saves time, and genes and their products can be tested extensively in isolation before use to ensure their safety (Halford, 2004). The technology leads to improved quality of food, increased yields and reduced prices of food.
Plants have been modified with short sequences of genes from the bacteria Bacillus thuringiensis (Bt) to express the crystal protein that Bt. produces. The genetically modified plants are thus producing the proteins to protect themselves from insects without any external application of Bt. and/or synthetic pesticide sprays. The production of Bt crops has been on the commercial scale since 1996. Some 29 million acres of Bt. cotton, corn, and potato were grown globally in 1999. The Bt. cotton protected the cotton industry and saved the United States some $92 million. By transferring the protein-coat gene of the zucchini yellow mosaic virus to squash plants that had previously sustained great damage from the virus, scientists were able to create transgenic squash plants with immunity to this virus.
This article was written by Charles Afriyie-Debrah, Marian D. Quain, Ruth N.A. Prempeh and James Y. Asibuo, CSIR-Crops Research Institute, Kumasi