Genetically Modified Organisms

Genetically Modified Organisms

Genetically modified Organisms or GMOs are defined as organisms whose genetic material or genetic constitution has been altered using recombinant DNA technology or genetic engineering.  Recombinant DNA technology that is now being routinely used in the molecular laboratories world over, involves the combining of DNA molecules from different sources and then introducing them into an organism. Hence the characteristics of an organism, or the proteins it produced can then be modified through alteration of its genes. It is important to point out that this term does not include organisms whose genetic makeup have been altered by conventional cross breeding or by “mutagenesis” breeding as these methods predate the discovery of the recombinant DNA technology.

Definitions of Genetically Modified Organisms on the Web

GMOs are plants and animals that have had their genetic makeup altered to exhibit traits that are not naturally theirs. Genes are taken (copied) from one organism that shows a desired trait and transferred into the genetic code of another organism.

A genetically modified organism is an organism whose genetic material has been deliberately altered. Examples are diverse, and include commercial strains  of wheat that have been modified by irradiation since the 1950s, transgenic experimental animals such as mice, or various microscopic organisms altered for the purpose of genetic research.

GMOs are a plant, animal, or microorganism produced or changed by genetic engineering.

Introducing a foreign gene into an organism which can propagate creates a genetically modified organism.

Life forms that are the result of combining the genes of one organism with that of another, thus altering the make up of the “target” organism.

The GMOs may not differ in appearance from non-GMOs e.g. Flavr-Savr tomatoes (these have delayed ripening and softening), Bt Corn (insect resistant), Freedom II squash (having resistance to the virus), Bolgard cotton (having resistance to insect pests) etc do not look different from their non GMO counterparts. However, we also have examples where the GMOs look different from their non GMOs counterparts for example glow in dark fish, housefly etc.

Among the GM crops, some may have improved taste or flavor e.g. GMO eggplants, others may have some additional features or improved qualities  like altered fatty acid content of soybeans or Vitamin A enriched golden rice or pigs with omega 3 fatty acids or even pest resistant crops. Some of the bacteria and  plants have been genetically altered and are being used for bioremediation/phytoremediation which is an area where microorganisms and genetically altered plants clean up pollutants from the environment. In some animals, organs are being genetically modified to use in organ transplants (xenotransplantation) e.g. pigs.

In some cases the definition of GMOs become a bit confusing. Not all seedless fruits are genetically modified. Techniques are available where by plants can be induced to bear seedless fruits by exposing their flowers to various concentrations and combinations of plant growth hormones. Using conventional breeding techniques also seedless varieties have been developed in certain plants such as bananas and watermelons. 

Theoretically GMOs can be developed using processes that occur naturally. These include

  1. Transformation that is defined as the uptake of foreign gene DNA by bacteria from the external environment.
  2. Transduction that involves the introduction of foreign gene to an organism using viruses as vectors.
  3. Plasmids that are extra chromosomal elements occurring naturally in the bacteria and yeast are also used as vectors.
  4. Enzymes that are derived from bacteria e.g restriction enzymes, ligases etc are also used in the making of GMOs.

Detection of GMOs may require a laboratory technique called Polymerase Chain Reaction (PCR)which helps to detect the introduced gene or the foreign gene in the recipient organism. However, the detection is possible only if the gene will remain intact therefore one cannot detect the gene in the processed foods that have incorporated the GMO products.

Tremendous efforts are going on to create healthier, cheaper and tastier products that are in demand all around the world. The genes from the roundworm C. elegans have been transferred to pigs to produce swine with significant increase in the amounts of omega-3 fatty acids.    Monsanto Inc. of St Louis and some other biotech farming companies like DuPont are developing omega-3-producing crops that yield healthier cooking oils. The attempts are being made to use genetically engineered pigs to study human disease especially heart condition. However, Federal regulators and the researchers have informed that as a precautionary measure, meat and dairy products rich in omega-3s will not be sold in supermarkets in the near future. The FDA is still considering Waltham, Mass based Aqua Bounty Technologies application for the permission to market a salmon genetically engineered to grow faster, which has been pending with the agency for a long time.

Often the most confusing aspect for the Biotechnology students is to know how does a GMO differ from one that is derived from conventional breeding?

Using the method of conventional breeding by reproduction, only individuals from the same species or related species can be mated to produce offspring. The offspring will have genes from both parents, but the genes are just different variants of the same genes coding for the same functions. As a GMO bypasses reproduction altogether, so completely new genes with new functions, as well as new combinations of genes can be introduced. However this can lead to the interaction of the organism’s own genes in unpredictable ways.

Conventional breeding involves crossing many individuals of one variety or species with another. The result is a population that preserves much of the initial genetic diversity of the parental lines, and selection occurs in successive generations until the desired results are achieved. It is therefore more controllable and predictable.

A transgenic line, in contrast, results from gene insertion events in a single original cell, out of which the entire line is produced.

 Furthermore, the genetic engineering process for making the GMO is uncontrollable and error-prone and it can cause random disturbances to the system, making the result highly unpredictable as well as unstable. Genetic instability of GMOs is now a well-known problem. Many GM crops are a failure and there are serious concerns regarding the GM animals.

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