29/10/2018

Genetically modified (GM) foods are foods derived from organisms whose genetic material (DNA) has been modified in a way that does not occur naturally (e.g. through the introduction of a gene from a different organism). Most existing genetically modified crops have been developed to improve yield through the introduction of resistance to plant diseases or increased tolerance of herbicides. It offers a time-saving method for producing larger, higher-quality crops with less effort and expense. Yet, such benefits must be balanced against the risks of changing the genetic makeup of organisms. What are those risks, and how likely are they to occur? In order to define them, we need to understand the science of plant genetic engineering.

 

For thousands of years, humans have been genetically enhancing other organisms through the practice of selective breeding. Look around you: the sweet corn and seedless watermelons at the supermarket are all examples of how humans have selectively enhanced desirable traits in other living things.

 

The type of genetic enhancement that generates the most concern goes a step beyond selective breeding, however. Technology now allows us to transfer genes between organisms. For example, the tomato plant's beetle resistance relies on a gene from a bacterium (Bacillus thuringiensis or Bt for short), which scientists inserted into the tomato plant's genome. This gene encodes a protein that is poisonous to certain types of insects, including the beetle.

As for how it’s done? Gene transfer technology is simply a sophisticated version of a cut-and-paste operation. Once the desired gene is identified in the native organism's genome, it can be cut out, transferred to the target plant, and pasted into its genome. Once the new gene has been introduced, the plant can be bred to create a new strain that passes the gene from generation to generation.

 

Genetic engineering, by contrast, involves the direct manipulation of DNA, and only really became possible in the 1970s. It often takes two different forms: There's "cisgenesis", which involves directly swapping genes between two organisms that could otherwise breed — say, from wheat to wheat – and then, there's "transgenesis," which involves taking well-characterized genes from a different species (say, bacteria) and transplanting them into a crop (such as corn) to produce certain desired traits.

 

Ultimately, genetic engineering tries to accomplish the same goals as traditional breeding, that is create plants and animals with desired characteristics. But genetic engineering allows even more fine-tuning. It can be faster than traditional breeding, and it allows engineers to transfer specific genes from one species to another. In theory, that allows for a much greater array of traits.

 

Now, let us come back to the above three scenarios:

 

1. For the tomato farmer, a biotechnology company introduces a new strain of tomato plant that produces a natural pesticide, making it resistant to the beetle. By switching to this new strain, you could avoid both the beetle and the chemical pesticides traditionally needed to fight it.

 

2. The family physician finds out about of a new approach that would reduce the cost to a fraction of its current price: genetically modified fruits and vegetables that contain various vaccines. By simply eating a banana, a child could be protected against disease without getting a shot!

 

3. The leader finds out about a biotechnology company that has genetically modified a rice plant that can thrive in salt water, providing your nation with the opportunity to feed its citizens while bolstering its economy.

 

Now that we’ve cleared the matter up for those three cases, it’s important that we consider the potential risks of GM foods as well. First up is the peril of cross-breeding with wild populations. For all of these examples, a primary concern is preventing genetically modified versions from mixing with the naturally existing populations of plants from which they're derived. Plants rely on the transfer of pollen, via insects or the air, to breed and produce offspring, and it's difficult to control how they cross-breed in the wild.

 

On the other hand, come to humans and there is the risk of toxicity or allergic reactions. Many people suffer from allergies to various food items, including nuts, wheat, eggs, or dairy products. There is concern that the protein products of introduced genes may be toxic or allergenic to certain individuals.

 

When farmers start growing genetically modified crops, they stop growing the old varieties. These old varieties are important sources of diverse genes that give plants other desirable characteristics. For example, a new pest or disease could come along and destroy the genetically modified rice. If one of the old rice varieties has a gene that makes it resistant, it could be cross-bred to make the saltwater rice resistant as well. If we lose the old varieties, we also lose their useful genes.

 

As for the impact on the environment, there's no easy answer since it often depends on the crops and how they're used.

In some cases, GM crops can help farmers use fewer chemical insecticides. In others, they might lead to greater herbicide use or pesticide resistance. On balance, many scientific bodies are unconvinced that GM foods pose a special environmental threat — so long as they're used carefully.

 

Here's what the National Research Council concluded in 2010: "Generally, GE crops have had fewer adverse effects on the environment than non-GE crops produced conventionally." But the report cautioned, "Excessive reliance on a single technology combined with a lack of diverse farming practices could undermine the economic and environmental gains from these GE crops."

 

The National Research Council also warned against improper use of GM technology: Farmers who plant herbicide-resistant GM crops often use a limited range of herbicides on their fields, which can give rise to herbicide-resistant "superweeds." Similarly, there's evidence that overplanting of Bt corn has fostered a new breed of resistant insects in some fields.