Gene Technology

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Genetically Modified Crops

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Genetically Modified Crops

Genetically modified plants are crops mutants whose part of their DNA has been altered, deleted, or added using genetic engineering techniques. The aim is to attain a crop with a specified enhanced or reduced characteristic especially in nutrient content of the crop.

Biological Basis

There are natural occurrences that facilitate genome transfer among organism species. Such occurrences happen in large scale with one known example being the emergence of genes that confer resistance to antibiotics in bacteria. The transfers are aided by retroviruses, retrotransposons, normal transposons, and any other genetic element that is mobile. These natural movements of genes promote the translocation of DNA fragments to new loci in the organism’s genome over time.

Development of genetically engineered crops involves forced addition or removal of DNA to the natural genome of a crop using modification techniques. The techniques applied in this case include electroporation, gene guns, Agrobacterium, and microinjection. Highly sensitive and efficient gene manipulation techniques of TALEN AND CRISPR are the recent developments in the domain of genome manipulation. TALEN (transcription activator-like effector nucleases) are a form of restriction enzymes made to cleave specified DNA sequences and are made by binding the TAL effector DNA binding domain and a cleavage domain. CRISPR are DNA fragment repeats common in archaea and bacteria that confer resistance to foreign elements and are used in the biotechnology technique of CRISPR/Cas9 for DNA editing to their potent deletion and addition mechanisms.

Use of gene guns is the most common technique and it involves shooting a crop of interest with particles of tungsten or gold which have been coated with DNA. The particles that are now under high speed pierce through the cell wall and the plasma membranes. The bound DNA gets separated from the metal and gets integrated in to the crop’s DNA. It has been successful in a number of cultivated crops especially monocots which have been less responsive to transformation with Agrobacterium. The major risk of this technique is that it can cause irreversible damage at the cellular level.

Gene addition with the use of Agrobacterium tumefaciens is another commonly used technique in the generation of GM crops. Agrobacteria naturally parasitize on plants and they insert their genes to the crop in the process. They transfer their own DNA to the host plant in a bid develop a favorable environment for their survival and the result is the proliferation of altered plant cells near the soil. The DNA sequence for proliferation of these cells is found in a circular plasmid called T plasmid. Engineering of crops using this bacterium requires deletion of this plasmid DNA and replacing it with the desired foreign gene. Thus, the bacterium acts as the channel of transportation of the foreign DNA into crops. This technique has been massively successful in dicots especially tobacco, tomatoes, and tomatoes.

Electroporation is convenient for gene editing in crop tissues that lack cell walls. The DNA fragments penetrate the host cells through tiny pores developed by means of electric currents. Microinjection directly infuses the DNA of interest into plant cells.

Tobacco plant has been greatly modified and it is used as a model in engineering research of other crop species. This is because of its acceptance of the transformation methods, its well analyzed genome, and ease of propagation. Introduction of new genes necessitate a promoter specific to the area of expression of the gene to avoid gene silencing. For example, to ensure gene expression in grains and not leaves of a rice crop, a promoter specific to endosperm is appropriate. The codon of the incorporated gene must be designed in a way that there is no predisposition to codon usage bias.

The methods of genome modification generate three major types of modifications in crops termed as transgenic, cisgenic, and subgenic GM crops. Transgenic crops have foreign genes from another different species which can be between the same kingdom are across kingdoms. Such genes have to undergo some slight modifications to guarantee expression in a correct and efficient manner in the tissues of the host crop. The genes are mostly for protein expression for example the BT (Bacillus thuringiensis) toxins, antigens used in vaccinations, and genes for herbicide resistance. Cisgenic crops are engineered using genes of the same species or those that have a close relation especially where close breeding is difficult. Subgenic crops are developed by means of gene knockout or knockdown to modify the genome of a plant without adding any foreign DNA for example there has been development of a subgenic wheat strain that is resistant to powdery mildew. The GM crop lacks genes that produce proteins involved in repression of defenses needed against powdery mildew.

Social and Ethical Implications

Altering the natural genome of crops in a bid to get a more beneficial crop has consequences that need to be evaluated before acceptance of the GM crop. In any case, such modifications can alter the crop’s growth rate, metabolism, and its interaction with abiotic factors. These outcomes affect not only the plant itself, but also the ecosystem in which it proliferate. Potential risks to the health of people include emergence of new allergens in genetically altered foods and in addition, transmission of antibiotic resistant genes to the gut microbial population.

There has been concern about the use of BT toxin in plants as form of biological control of pests. For example BT corn has recombinant genes that confer resistance to attack by pestiferous insects. This has been used for years as an environmental friendly insecticide with the benefit being a reduced usage of chemical pesticide in farms. Sadly, seeds with recombinant genes expose non-target organisms to strange toxins in the environment.

Another concern on the development of GM crops is that private research organizations claim rights of any organism that they develop and fail to share them at a favorable price with the general public. Such practices affect negatively on the economy by allowing moneyed farm production centers to dominate while wiping out small-scale farmers who cannot afford the improved seeds.

Besides, even if the GM seeds and other propagates are shared in a fair manner, some people would still reject them due religious or other personal reasons. The ethical issue here is a debate on whether it is right with God as well as addition of materials into foods that are avoided due to religious restrictions. Some people have this notion that altering the natural genetic makeup of any organism is wrong and immoral.

Regardless of this ethical debates, GM crops still have massive benefits as highlighted by food security campaign programs. Food supply become predictable and can be speculated and there is enhanced nutritional value of crops. Genetically engineered foods also tend to have longer shelf life as compared to the normal unaltered ones. There is this process, “pharming”, that allows production of vaccines and vital proteins through modification of plants and this is a cheaper alternative of improving personal health. Last but not least, the GM crops reduce the usage of pesticides and insecticides whose accumulation in the food chain result to health complications of organisms.

Personal Viewpoint

GM crops are of immense benefit in promoting food security across the globe. Plants that are greatly susceptible to attack by pests can now be improved to become resistant and in effect increase production. With changing climate that threaten to complicate the survival of humans and other species, any farming method that guarantees food safety is held in great respect and need to be supported by governments and humanitarian organizations.

The argument that such technique are meant to correct God’s creation should be treated with disdain because God gave us brains to work and improve the creation in the quest for our survival. Our knowledge comes from God and its application depicts appreciation of this God-given blessing. Regarding the ecological imbalance that result from some of the genome modifications, artificial optimization of ecological equilibrium is very much possible. Furthermore, the benefits of GM crops far outdo their malefits.

References

Crow, J. F. (2012). Gene therapeutics: methods and applications of direct gene transfer. Springer Science & Business Media.

David, K. &. (2011). What can nanotechnology learn from biotechnology?: social and ethical lessons for nanoscience from the debate over agrifood biotechnology and GMOs. Academic Press.

Hull, R. T. (2009). Genetically modified plants: assessing safety and managing risk. Academic Press.

Letourneau, D. K. (2001). Genetically engineered organisms: assessing environmental and human health effects. CRC press.

Yamamoto, T. (2014). Targeted Genome Editing Using Site-Specific Nucleases. Japan: Springer Tokyo Heidelberg New York Dordrecht London.




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