Introduction

Farmers have been modifying plant and animal species for thousands of years. If you have planted a garden or flower beds, you have taken advantage of genetic modification practices. At the garden center or in the seed catalog you chose, for example, plants that are the “healthiest” looking, with the most vibrant colors. These chosen plants then will proliferate, and possibly produce seeds that pass along those traits. Farmers cross breed varieties of animals and plants for the same reasons (desired traits) and in much the same way (selective breeding). For example, the strawberry we consume today is a cross between a native variety from North America and a variety from South America.

Learning

What is Genetically Engineering?

While farmers have been improving plants and animals through selective breeding for thousands of years, more recently we have found another way. Genetic Engineering (GE) can also be used to improve organisms, most commonly plant crops. GE uses biotechnology to alter the genetic code by inserting genes into it that introduce a new desirable trait. In many cases, the desirable traits reside in one species and are transferred into another species. When you insert genes from one species into another species, the result is referred to as a transgenic organism. Genetically modified organism (GMO) is a broader term referring to transgenic organisms as well as to organisms whose DNA was modified but no species to species transfer took place.

Let us examine a few examples of transgenic organisms (or GMOs).

A) Insect Resistance

Bacillus thuringiensis is a soil bacterium that has a gene that produces a toxin that is lethal to several insects. The toxin gene (referred to as the Bt gene) is then inserted in a plant genome and the plant now makes the toxin. Therefore, as an insect snacks on the plant the toxin in the plant kills the insect. These crops have improved yield (produce more fruit, for example) and there is less need to spray insecticides. This results in less costs and reduces possible health effects of excess insecticide. In the United States over 90% of soy, and over 80% of cotton and canola products come from genetically modified versions of the crops.

B) Improved Nutritional Quality

Rice is the staple food for a large portion of the world’s population. In the process of preparing rice for consumption, it is milled. Milling removes the outer husk and any beta-carotene it contained leaving only the seed endosperm (otherwise known as the rice kernel as we know it). Beta carotene is the precursor to vitamin A. Therefore, it is not surprising that in the countries where rice is a major segment of diets there is vitamin A deficiency. In January 2000, a group of researchers reported that they had succeeded in incorporating the three genes into rice that enabled the plants to manufacture the beta-carotene in the seed endosperm (the part we typically eat). As a result, the rice was now colored yellow by the beta carotene (similar in color to other high beta carotene foods, like carrots).

C) Herbicide Resistance

Weeds, whether on a lawn, a home garden, or on a large farm, are often desired to be removed. Chemicals, specifically herbicides can be applied to kill the weed species. Questions have been raised about the safety — both to humans and to the environment — of some of the broad-leaved weed killers like 2,4-D. There are other types of chemicals on the market, but they also damage the wanted plant species. Genes have been inserted into crop plants that make them resistant to the herbicide, therefore when applied to the fields, the weeds die off, but the crop is not affected.

Controversies

The introduction of transgenic crops into agriculture is a controversy in many countries. The issues that have been brought up:

• The potential risk of the inserted genes in commercial crops endangering native plant species. For example, the concern that the herbicide resistant gene placed in a corn crop escaping to a weed species therefore a weed would now be resistant to the chemical manufactured to kill it.
• The gene for Bt toxin gene inserted into a crop and the pollen from that crop killing pollinators like honeybees, which are not the intended target.

Studies have been done and are continuing regarding these issues. To date no data has been collected that confirms these worries are actual issues. In addition, studies have been done testing whether transgenic foods are a threat to human health. No data has been found to support that concern.

Summary

GMO – a genetically modified organism, which includes transgenic organisms

Transgenic organism – an organism where genes from one species is transferred into another species.

Bt gene – from a species of soil bacteria, makes a toxin that kills insects.

Yellow (Golden) rice – four genes inserted into rice, so they now make beta carotene a precursor to vitamin A.

Herbicide resistance – when a gene is inserted into a crop that allows that crop to NOT be affected by a herbicide.

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Sources:

Regulation of Plant GMOs. (2021, January 3). Retrieved May 27, 2021, from https://bio.libretexts.org/@go/page/39527

Crops, Genetics, and GMOs. (2019, June 2). Retrieved May 27, 2021, from https://bio.libretexts.org/@go/page/21490

Genetically Modified Organisms (GMOs). (2021, March 6). Retrieved May 27, 2021, from https://bio.libretexts.org/@go/page/13342

Transgenic Plants. (2020, December 31). Retrieved May 27, 2021, from https://bio.libretexts.org/@go/page/4926

Bacillus Thuringiensis. (2020, December 31). Retrieved May 27, 2021, from https://bio.libretexts.org/@go/page/5975

CSIRO ScienceImage 7410 A larva of Helicoverpa armigera the world’s worst insect pest.jpg. Digital Image of a larva an Insect pest. Sept 19, 2014. Wikimedia Commons/ CC-BY-SA-3.0

Golden Rice.jpg. Digital Image of Yellow Rice. Feb 15, 2011. Wikimedia Commons/ CC-BY-SA-2.0

GMOs and Patents: Part 1 – Terminator Genes. (Dec 8, 2015). Retrieved May 27, 2021, from https://biofortified.org/2015/12/gmos-and-patents-part-1-terminator-genes/