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Unintended Effects of Genetic Manipulation

Type of Unintended Effect: Morphological (Animals)


Atlantic salmon expressing transgenic growth hormone experienced numerous changes to their cardiorespiratory system.

Atlantic salmon expressing transgenic growth hormone experienced numerous changes to their cardiorespiratory system.

Transgenic coho salmon expressing growth hormone had enlarged heads, reduced viability, and accelerated development of their life cycle.


Transgenic pigs expressing bovine growth hormone had lower appetites, enlarged organs, gastric ulcers, and other health problems.

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

Transgenic pigs with elevated levels of growth hormone were infertile, pre-diabetic, and experienced joint problems.

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


Transgenic expression of sheep growth hormone in sheep increased the incidence of reproductive problems and premature death.


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

Type of Unintended Effect: Morphological (Plants)


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


Apples over-expressing a fruit-ripening enzyme lacked flowers and had malformed stomata and altered composition of cell walls.


Plants producing a biodegradable polyester were smaller, never produced seeds and showed severe changes in metabolism.

Suppression of DHS enzyme in Arabidopsis (a mustard plant) was associated with enlarged leaves, greater root mass, and enhanced seed yield.


Barley expressing a heat-stable enzyme showed highly variable expression of the enzyme, an anomalous distribution of expression in the grain, and dramatically reduced weight of individual grains.

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


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.


Glyphosate-resistant cotton showed abnormal reproductive development when sprayed with glyphosate.

Fruiting morphology was altered when glyphosate-resistant cotton was sprayed with glyphosate.


Dandelions manipulated to have compound leaves showed irregular leaf form and did not flower.


Insect-resistant transgenic potatoes had less foliage and altered levels of leaf-glycoalkaloids.


Bt rice showed signs of dwarfism and other abnormalities.


Herbicide-resistant soybean plants were shorter, with less chlorophyll, lower weight, and increased susceptibility to stem-splitting at high temperatures.


Lectin transgene for stemborer resistance alters growth of sugarcane.


Discoloration and DNA rearrangements were observed in transgenic tobacco plants expressing HIV proteins.


Tomato plants overexpressing phytoene synthase gene were stunted in growth.

Suppression of DHS gene in tomatoes was associated with lack of fruiting, altered leaf morphology, higher rate of photosynthesis and other changes.

Transgenic tomatoes altered with a marker gene construct showed significant changes in morphological and physiological characteristics.


Spring wheat with scab-resistance transgene was not scab resistant and showed localized death of leaf tissue.

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

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