Pros and Cons of GMO crops

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Rashmeen Jaggi

Science Report – 10B

11th March 2010

Are we harvesting Fear or Hope?

The Pros and Cons of GM Crops

Since 1996, when the first genetically modified crops were commercialized, the use of genetically modified crops has increased by 10% or more each year and this estimation is likely to increase in the coming years. These crops are being utilized for both animal and human consumption, which has been increasing with the massive increase in world population. Genetically modified crops are created in the process of genetic engineering by inserting a foreign gene into the genome of the organism in order to increase resistance against pest and pesticides that have been causing crop loss for centuries. This scientific approach is now in use by approximately 8.5 million famers around the world; 90% of them living in developing countries. The use of genetically modified crops has not only benefitted the international market but has also allowed scientists to recreate species that have had previously been extinct. Unlike natural selection or selective breeding, genetic engineering has allowed more predictable and improved results. 7, 8 & 12

   

Figure 1: The above demonstrate a DNA molecule which is composed of four different types of nucleotide basis that are paired together forming the following pairs: adenine-thymine and cytosine-guanine. The basis could be either paired as A: T or T: A and C: G or G: C; abbreviations for the four bases. 14, 16 & 17

Genetic engineering is the formation of a whole new range of genes, proteins and new organisms, through the use of one out of the three different methods. An existing gene can be either altered or turned off or instead, could be replaced by a foreign gene in the process of genetic engineering. This exchange of genes among different organisms is only possible due to the universal genetic code which is a specific sequence of nucleotides in DNA or RNA that determine the characteristics and the functioning of an organism. A gene, which is the physical unit of heredity, contains a molecule that decides the function and structure of all organisms, called the DNA. The DNA molecule is made up of four different nucleotide basis that are linked up together in pairs within a long string, forming a code. Whether it is a blade of grass or a human being or a pond scum or an insect, their DNA consists of the same nitrogenous bases (figure 1), but arranged in a different sequence. Changing the order of the nucleotides would create different organisms from different species with different characteristics. Having a universal code for all organisms allows the scientists to be able to exchange different genes among organisms of different species in order to create a new organism or range of genes & proteins, without any complications. 4, 14 & 20

As previously mentioned, genetic engineering involves three different methods where either an existing gene can be altered in order to improve its performance so as to express it at a higher level; e.g. growth hormones, or an existing gene could be deactivated to prevent a particular expression of the trait, or where another foreign gene could be inserted into the genome to enable the organism to express the desired trait. These three methods could be used for different purposes and in different circumstances. Gene therapy is a technique involving altering or deactivating an existing gene in order to correct a faulty gene that leads to disease development in an organism. The gene could be repaired by various methods which either involve changing the limit to which a gene could be turned off or on, or swapping an abnormal gene for a normal one, or repairing an abnormal gene via selective reverse mutation. Gene therapy allows encoded proteins to perform normally and carry out functions which once seemed impossible for the organism. 1 & 3

Figure 2: The above is a demonstration of how a restriction enzyme cuts up a DNA molecule, leaving behind equally parted recognition sites. Sometimes the recognition sites could be overhanging “sticky end” or non-overhanging “blunt end”, depending on the restriction enzyme. 1, 18 & 19

Unlike gene therapy, gene cloning focuses on making large quantities of a piece of a desired DNA that has been isolated from cells that grow in science laboratories. Genetically modified crops are created via gene cloning which involves adding a foreign gene into the host DNA and then duplicating the resultant gene. This technology is not yet adopted by all countries around the world, mainly because of its expense and high scientific requirements. In order to clone a gene, a DNA is first extracted from a desired gene and then is cut up in a controlled manner using a restriction enzyme. Restriction enzymes are molecular scalpels that are capable of cutting up a double stranded DNA molecule into very exact sequences of 4 to 8 base pairs known as the recognition sites, which may either result in sticky ends or blunt ends (figure 2). Both, the DNA and the plasmid (it is a vector; DNA molecule that transports foreign genetic material into another) are cut up using the same restriction enzyme so as to produce similar sticky ends. Using DNA ligase in the process of ligation, the sticky ends of the two are recombined by base-pairing known as annealing to produce a recombinant plasmid. Once joined together, the recombinant plasmid is then introduced into a bacterial cell by inserting it to a bacterial culture. This plasmid will then be accepted by the bacteria in the process of transformation, under appropriate conditions. The actual cloning process takes place only if the bacteria cell containing the recombinant plasmid is ready to reproduce. Once ready, then the recombinant plasmid replicates independently inside the bacterium to produce many copies of the target gene. 1

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As stated earlier, genetically modified crops are created using the above method. Unlike selective breeding or natural selection, the results for genetic engineering are more predictable as when creating genetically modified crops, DNAs of two different species with impressive traits are combined together to produce high quality and fully resistant to pests and pesticides, crops. However in this case, the recombinant plasmid is straight away introduced into the plant cells where it combines with the plant’s chromosomal DNA. Later, before being planted out to grow normally, these transformed plant cells are grown by tissue culture. Fine examples of a GMO ...

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