The Unintended Effects of Genetic Engineering

Executive Summary


The Nature Institute, a non-profit educational research institute located in upstate New York, has documented evidence, of more than a hundred studies; published primarily in the peer-reviewed literature; revealing the unintended consequences of genetic engineering on more than thirty-five different species of plants and animals, including humans.

Distilling a voluminous technical literature, The Nature Institute has summarized both the intended and unintended consequences of transgenic experiments. The emerging picture tells a dramatic story – one that, to date, has scarcely begun to inform the public conversation about genetic engineering.

Types of Unintended Effects

  1. Effects on Food and Feed Quality
  2. Physiological Effects
  3. Morphological Effects (Changes in Behavior)
  4. Effects on the Environment

You Can’t Fool Mother Nature

Luther Burbank did not develop the russet potato by using the techniques of genetic engineering; neither did Herbert Mendel, the father of modern genetics, or Norman Borlaug, the father of the Green Revolution.  Genetically engineered plants are formed by laboratory methods of genetic recombination to bring together genetic material from multiple species, creating genetic sequences that would not otherwise be found in the genome itself. For example, genetically engineered ‘Bt’ corn is produced by taking DNA from bacillus thuringiensis, a bacteria belonging to one domain (Bacteria); and engineering it into corn, belonging to another domain (Eukarya). Unlike traditional breeding or hybridization, genetic engineering takes place outside the natural reproductive context, by forcibly violating the natural barriers that exist between species.

Much of the debate concerning genetically engineered organisms, their widespread use in animal and human food, and their impact upon the environment could be raised to an entirely new and more productive level if certain facts were more widely known.

When a genetically engineered organism is invented and introduced into the environment, unintended and unexpected effects are also created.

1)   When DNA is imported from one species to another (or when the DNA of a single organism is genetically engineered), the physiology and behavior of the organism are altered.

2)   The quality of the food and feed produced from genetically engineered seed is affected.

3)   Animals and humans who eat genetically engineered food and feed are affected in unpredictable and harmful ways.

4)   The genetically engineered seed passes its man-made genetic code to future generations. Unlike a horse and a donkey which, when mated, produce sterile offspring (mules), genetically engineered seed remains forever capable of reproducing itself, contaminating the genetic pool of all future generations.

Non-target effects have proven extensive and wildly unpredictable. The evidence is not disputable or even particularly controversial.  It’s simply not widely known, as it much of it remains buried in the technical literature. However, once it is known, the frequently heard claim that the genetic manipulation of organisms is a “precise science” without dramatic risk, will no longer be made.

 The Nature Institute documented the unintended effects of genetic engineering on more than thirty-five species of plants and animals, including humans. It collected examples from the scientific literature and wrote short reports on each example. The compilation is by no means exhaustive, as the literature still to be reviewed is extensive.  Their list of more than eighty published studies is available on the Nature Institute website at:

By clicking on the title of each report, one can view the intended (‘target’) effect of each transgenic experiment, the unintended (‘non-target’) results, how the project was funded, author affiliations, and the commercial status of the genetically engineered organism:

In Alphabetical Order by Species:

Alfalfa:  Plant height and flowering were altered in alfalfa genetically engineered to reduce lignin content.

Alfalfa:  Genetically engineered alfalfa with corn transgenes for anthocyanin (red-purple pigment) production was not visibly altered or changed dependent on light and temperature conditions.

Apple:  Apples genetically engineered to over-express a fruit-ripening enzyme lacked flowers and had malformed stomata and altered composition of cell walls.

Aspen Trees: Innate immunity is affected in aspen trees genetically engineered for insect-resistance.  

Bacteria:  Genetically engineered root nodule bacteria with Bt transgene tended to displace non-manipulated bacteria in legume root nodules.

Barley:  Genetically engineered barley plants over-expressing a zinc transport protein had smaller seeds and did not accumulate more zinc when grown in zinc-deficient soil.

Barley:  Genetically engineered barley with the transgene for a heat-stable enzyme showed highly variable levels of the enzyme, an anomalous distribution of expression in the grain, and dramatically reduced weight of individual grains.

Barley:  Difficulties were encountered when trying to genetically engineer human collagen in barley.

Barley:  A group of genetically engineered barley plants expressing the bar selectable marker gene did not produce viable offspring.

Bees:  Genetically engineered sugarbeet production alters population densities of some arthropods, significantly reducing the number of bees and butterflies in sugar beet fields.

Bees:  Fewer wild bees were observed in genetically engineered canola fields.

Bentgrass:  Spread of herbicide-resistance from genetically engineered creeping bentgrass into the wild.

Birch Trees:  Genetically engineered birch trees expressing an antifungal enzyme from sugarbeets showed increased susceptibility to leaf spot disease in the field.

Butterflies:  Monarch butterfly larvae exposed to anthers from genetically engineered corn ate less and gained less weight.

Canola:  Transgenes that have escaped from genetically engineered canola can persist in the wild. 

Canola:  Herbicide-resistant canola volunteers were still detected after ten years of stringent control.

Canola:  Conventional, certified canola seedlots were contaminated with genetically engineered seeds.

Canola:  Genetically engineered canola plants over-expressing a bacterial phytoene synthase gene also had a reduced level of chlorophyll, changed structure of plastids, changed composition of fatty acids, and delayed germination.

Canola: Experimental cross-pollination between genetically engineered herbicide-resistant canola and wild filed mustard led to highly fertile, herbicide-resistant wild field mustard. 

Cotton:  Genetically engineered cotton showed decreased ability to kill cotton bollworm larvae during flower development and flowering.

Cotton:  Cotton plants and seeds expressing Bt toxin were found in non-Bt refuges.

Cotton:  Insect-resistant, genetically engineered cotton was more susceptible to fungal disease than its parent line.

Corn:  Genetically engineered corn varieties matured more slowly and had on average lower grain yield and higher grain moisture content than conventional varieties. 

Corn:  Genetically engineered corn had changed lipid composition in stems; also, lipid composition in soil was altered, and soil respiration was reduced. 

Corn:  The transgenic sequences of some genetically engineered corn plants have changed since they were approved.

Dandelions:  Dandelions genetically engineered to have compound leaves showed irregular leaf form and did not flower.

Humans:  Transgenic DNA from glyphosate-resistant soybeans was detected in the intestinal flora of humans.

Fish:  Tilapia fish engineered for transgenic expression of growth hormone had deformed heads and backs, atrophied gonads, and lower mineral content.

Flowers:  Single-site integration of foreign DNA into arabidopsis showed rearrangements and deletions of both plant DNA and foreign DNA.

Flowers:  Unintended changes in gene expression were observed in arabidopsis plants engineered for resistance to the herbicide glufosinate.

Flowers: Over expression of phytoene synthase gene in arabidopsis resulted in delayed germination, increased levels of chlorophyll, and changes in relative levels of carotenoids.

Insects:  Byproducts from genetically engineered corn affected stream insects.

Mice:  Diet containing genetically engineered soybeans affected the nuclei of liver cells in mice.

Oats:  Insertion of transgenes in oats resulted in modification of both the transgenic construct and host DNA.

Peas:  Peas engineered to be weevil-resistant elicited immune reactions in mice.

Pea:  Peas engineered to be weevil-resistant had lowered starch digestibility when fed to chickens and pigs.

Pig:  Genetically engineered pigs with elevated levels of growth hormone were infertile, pre-diabetic, and experienced joint problems.

Pig:  Genetically engineered pigs expressing bovine growth hormone had lower appetites, enlarged organs, gastric ulcers, and other health problems.

Pig:  Transgenic expression of a mouse milk protein impaired mammary development and function in pigs.

Pig:  Sheep growth hormone expression was highly variable in genetically engineered pigs, whose bodies had more protein and water and less fat.

Pineapple:  Pineapple plants genetically engineered with transgenes for fungus and herbicide resistance had altered biochemical make-up.

Potato: Genetically engineered potatoes with altered sugar metabolism had changed levels of many metabolites, some not thought to be associated with sugar metabolism.

Potato:  Potatoes genetically engineered to store inulin had higher alkaloid content.

Potato: Potatoes genetically engineered to store more starch stored less starch.

Potato: Genetically engineered potatoes with transgene for virus resistance were variably resistant, and some lines without the target gene nevertheless became highly resistant.

Potato:  Potatoes genetically engineered for insect-resistance had less foliage and altered levels of leaf-glycoalkaloids.

Rice:  Genes escaped from cultivated genetically engineered rice to its weedy and wild relatives.

Rice:  Genetically engineered rice showed signs of dwarfism and other abnormalities.

Rice:  Rice genetically engineered with a disease-resistance gene activated the oxidative-stress response.

Salmon:  Genetically engineered coho salmon expressing growth hormone had enlarged heads, reduced viability, and accelerated development of their life cycle.

Salmon:  Genetically engineered Atlantic salmon expressing transgenic growth hormone experienced numerous changes to their cardiorespiratory system.

Salmon:  Coho salmon genetically engineered for transgenic expression of growth hormone led to a narrower body, more red muscle mass, and smaller white muscle fibers.

Salmon:  Coho salmon genetically engineered for transgenic expression of growth hormone were more aggressive predators in simulated natural environments.

 Sheep:  Sheep genetically engineered for transgenic expression of growth hormone had increased incidence of reproductive problems and premature death.

 Sheep:  Genetically engineered sheep had unusually high morbidity and expressed a milk-specific protein in their spleen, liver, and other organs.

Soybean: Genetically engineered soybean plants were shorter, with less chlorophyll, lower weight, and increased susceptibility to stem-splitting at high temperatures.

Soybean:  Root colonization of genetically engineered soybeans by pathogenic Fusarium fungi increased with glyphosate application.

Sunflower:  Wild sunflowers genetically engineered with transgene for Bt toxin produced more seeds than normal wild sunflowers.

Sugarbeet:  Genetically engineered sugar beets became more susceptible to root rot when sprayed with glyphosate.

Sugarcane:  Genetically engineered sugarcane plants with lectin transgene for stem borer resistance showed altered growth.

Sugarcane:  Sugarcane engineered to reduce polyphenol oxidase (PPO) activity had greater PPO activity, even without the transgene.

Tobacco:   Discoloration and DNA rearrangements were observed in genetically engineered tobacco plants expressing HIV proteins.

Tobacco:  Genetically engineered tobacco with resistance to bleaching herbicides had altered composition of carotenoids.

Tomato:  Genetically engineered tomatoes had altered levels of at least fifteen other substances.

Tomato:  Genetically engineered tomatoes altered with a marker gene construct showed significant changes in morphological and physiological characteristics.

Tomato:  Genetically engineered tomato plants over expressing phytoene synthase gene were stunted in growth.

Weeds:   Increased planting of genetically engineered crops and application of glyphosate causes increase in glyphosate-resistant weed species.

Wheat:  Genetically engineered wheat transformed with a high-molecular-weight glutenin gene showed irregular expression of glutenin and changed its expression levels over subsequent generations.

Wheat:  Genetically engineered spring wheat with scab-resistance transgene was non scab-resistant and showed localized death of leaf tissue.

Wheat: Genetically engineered wheat outcrosses more often than conventional wheat of the same varieties.

Wheat:  Genetically engineered wheat expressing transgenic glutenin shows reduction in yield, varying production of glutenin, and altered morphology.


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