Genetically Modified Foods. Creating a GMO

Genetically modified (GM) foods are foods that are, or are made from, organisms that have been modified using biotechnology. Such genetically modified organisms (GMOs) contain alien genes, also called "transgenes," that are taken from plants, animals bacteria, or viruses, or that were created synthetically in a laboratory.

Genetic engineers have harnessed the mechanisms adapted by bacteria and viruses to overcome the defenses that nature designed to protect individual genomes (an organism's genetic material) from invasion by foreign DNA. This allows engineers to insert novel genes that confer a commercial advantage for agricultural production.

These genes include those for traits such as herbicide tolerance, pest resistance, ability to grow faster and bigger, delayed ripening, longer shelf life, and higher oil content. Biotechnology is also being used to convert plants and animals into factories for producing drugs and other products. This is referred to as "biopharming."

Although there are alternate methods of achieving the same food production goals, methods that pose none of the same risks to human health and the environment that GMOs do, bioengineers producing GM foods claim that such foods offer a safe alternative to agricultural chemicals and are necessary to feed the world's expanding human population.

GM foods raise a myriad of issues related to the safety of human health and the environment, as well as to economics, politics, public policy, and international trade relations. They are highly controversial and have been dubbed with contrasting labels from "Frankenfoods" by anti-GM groups to "super crops” by pro-GM groups. Consumers get mixed messages about GM foods, and nations are polarized in their acceptance or rejection of GMOs.

Creating a GMO. In genetically engineered foods, a gene from a foreign species (virus, bacterium, animal, or plant) or a synthesized gene (one that is constructed or modified in a laboratory and does not occur in nature) is linked to a reporter gene (often for antibiotic resistance) that signals successful insertion of the alien DNA, and to other viral or bacterial DNA sequences necessary for insertion and expression of the gene in the host genome.

The resultant cassette of chimeric DNA is spliced into a bacterial plasmid, which is used to create multiple copies of the transgenic construct. Then the cassette is inserted into a viral or bacterial carrier that is introduced into the host plant or animal. Other methods for introducing the foreign DNA include, for animals, injection directly into an egg, or, for plants, either the use of a gene gun to shoot the DNA into a group of plant cells or electroporation, which uses electric shock to trick the host into allowing passage of the alien DNA through the cell wall.

Transformed cells are then grown into organisms by cloning or tissue culture. The term for a successful transformation is an "event." The only GM animal product currently approved for the U.S. market is recombinant bovine growth hormone (rBGH), which is injected into cows to stimulate milk production. A number of GM crop plants, however, are being grown in the United States and other countries. Consequently, over 60 percent of food products on American grocery store shelves contain genetically modified material.

Unless it is either produced from organically grown crops or imported from a country where GM foods are either labeled or banned, almost every processed food product in the United States contains some ingredient derived from GM corn, soybeans, or canola. Corn and soybeans, which are the most widely grown economic crops in the United States, are incorporated almost universally as ingredients of processed foods. Most consumers in the United States are consequently not aware of the extent to which they are consuming GM foods.

Advocates of GM foods claim that genetic modification of plants and animals is not new because humans have been artificially selecting desirable traits in plants and animals for thousands of years. Humans saved the seed of the most productive and delicious plants and used prime animals for breeding. Genetic engineering, however, is vastly different from conventional plant and animal breeding methods because it allows scientists to insert a gene or genes from virtually any organism into any other organism.

A description of how a type of GM corn is developed illustrates the difference between conventional methods that select traits for improving crops through natural recombination in sexual reproduction and genetic engineering that transfers one or more alien DNA sequences using the tools of biotechnology.

GM Corn Example. The worst insect pest of corn in the United States is rootworm, the larval stage of a beetle. The underground larvae feed on the roots of developing corn plants and can cause up to 50 percent reduction in grain yield. The total costs to growers are over $1 billion a year in crop losses and insecticide costs. Biotechnology companies have developed a genetically engineered rootworm-resistant corn by inserting a gene from the bacterium Bacillus thuringiensis (B.t.).

This B.t. gene, referred to as cryBbl, codes for a potent enzyme that breaks down the insect digestive system. Approval for commercial use of Monsanto's GM root- worm-resistant com, referred to as "MON 863," is pending. MON 863 contains various DNA sequences from three types of bacteria, as well as from a virus, wheat, and rice.

The DNA sequences are spliced together, cloned in a bacterial plasmid that was then cut with a restriction enzyme (molecular scissors), coated to form metal beads, and shot into corn cells with a gene gun. The cells are then placed in an antibiotic- containing medium because only cells that have successfully received the gene to make them resistant to antibiotics can grow there. Those transgenic cells grow into rootworm-resistant corn plants.

The MON 863 plants are then cross-pollinated with inbred lines to incorporate the GM trait into the commercial production pipeline. Analysis of this GM corn reveals changes in its nutritional composition when compared to conventionally bred corn.

There is an increase in levels of the essential amino acids cysteine, aspartic acid, and glycine; there is a decrease in the amino acids leucine, phenylalanine, and glutamic acid; and there is also a decrease in the other important nutrients phosphorous, magnesium, zinc, manganese, vitamin E, and phytic acid. This illustrates how, along with the introduction of novel DNA sequences, GM crops have altered compositions from their original, non-GM counterparts.

 






Date added: 2023-08-28; views: 163;


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