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Unintended Effects of Genetic Manipulation

Intended Effect: Enhanced Growth (Animals)


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

Genetically modified atlantic salmon/brown trout hybrids have unexpected ecological effects.

Transgenic expression of growth hormone in coho salmon led to a narrower body, more red muscle mass, and smaller white muscle fibers.

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

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


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 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.

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