By Paul Jackson


There have been numerous arguments for and against the use of genetically modified organisms, GMOs, in many quarters. While genetic engineering has been part of drug manufacturing for a long time, it is the use of these techniques in food production that appears to be generating a lot of jitters. Transgenic organisms appear to generate even more controversy owing to the fact that they have genetic material obtained from other species. In a bid to get safer products, researchers are now considering using a genetically engineered organelle.

The nucleus has been the main target for genetic modification for many years. With advancing research, it has become evident that a number of processes can be undertaken on other organelles to achieve the same results. The organelles that have emerged as the most ideal are chloroplasts and mitochondria. Chloroplasts are only present in plants but mitochondria can be found in both plants and animals cells.

Mitochondria are considered the powerhouse of the cell. They produce energy necessary for most of the cell processes through a process known as oxidative phosphorylation. If they fail, the cell is at risk of dying since the alternative energy production pathways can only sustain it for a limited duration of time. Mitochondria posses a genome just like the nucleus. Their genome is, however, a lot smaller.

One of the theories that have been advanced to explain the presence of genetic material in mitochondria proposes that they were initially independent primitive organisms. They were largely parasitic depending on other unicellular organisms for most of their functions. As they evolved over thousands of years, some of their genome was lost and they could, therefore, not exist on their own. They entered the cell and started a symbiotic relationship. This theory has also been used for chloroplasts.

Chloroplasts are vital to the process of photosynthesis. This is a process that occurs in green plants and involves the use of sunlight energy in food production by a plant cell. These structures have also been established to also play a vital role in processes such as fatty acid synthesis, amino acid synthesis and mounting immune responses by the cells. Chloroplasts posses a DNA that takes on a circular conformation in most cells. Genetic modification of this DNA is passed on to daughter cells through inheritance.

Genome modification involves several steps. The first is gene isolation. This is where the desired gene is identified and obtained either from another cell or by synthesis. Several copies of genes have been studied and isolated and are now available in the genetic library. This may serve as an alternative source. Addition of various elements such as promoter and terminator regions makes the gene active.

The next step involves insertion of the isolated gene into an organelle (mitochondria or chloroplast). If the targeted cell is a bacterium, processes such as electric shocking and thermal stimulation may be required. In animal cells, the most common technique is known as microinjection. Those used in plants include antibacterial mediated recombination, electroporation and biolistics among others.

When genetic material is introduced into a cell, it is only this cell that is effected. There is a need to propagate this cell so as to make sure the effects are evident at the level of the organism. This is usually achieved by taking plant cells through a process known as tissue culture. In animals, stem cells are provided with favourable conditions for cell division. The cells are studied to ensure that the transfer process has taken place.




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