O What Is The Trojan Gene Effect And What Is The Concern Over Genetically Modified Animals?

April 2000

Transgenic fish could threaten wild populations

West LAFAYETTE, Ind. – Purdue University researchers have establish that releasing a transgenic fish to the wild could damage native populations even to the point of extinction.

A transgenic organism is one that contains genes from another species. The Purdue research is part of an endeavor past Purdue and the U.S. Department of Agriculture to assess the risks and benefits of biotechnology and its products, such as genetically modified fish. The study was published in November in the Proceedings of the National University of Science.

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Purdue fauna scientist Nib Muir and biologist Rick Howard used minute Japanese fish chosen medaka to examine what would happen if male person medakas genetically modified with growth hormone from Atlantic salmon were introduced to a population of unmodified fish. The research was conducted in banks of aquariums in a laboratory setting.

The results warn that transgenic fish could nowadays a significant threat to native wild animals. "Transgenic fish are typically larger than the native stock, and that can confer an advantage in attracting mates" Muir says. "If, as in our experiments, the genetic change also reduces the offspring's ability to survive, a transgenic fauna could bring a wild population to extinction in twoscore generations."

Extinction results from a phenomenon that Muir and Howard call the "Trojan gene hypothesis." By basing their mate selection on size rather than fitness, medaka females choose the larger, genetically modified just genetically inferior medaka, thus inviting the subconscious hazard of extinction.

The transgenic medaka were produced by inserting a gene construct consisting of the homo growth hormone driven by the salmon growth promoter into medaka. The viability of groups of modified and conventional fish were measured at 3 days of age, and xxx percent fewer transgenic fish survived to that age. The researchers calculated that big males had a four-fold mating advantage, based on observations of wild-type medaka. Computer models then were used to predict the consequences of the transgenic mating advantage combined with the reduced viability of the young.

The written report represents scientists policing scientific discipline, Muir says. "I promise people understand that scientists are investigating the risks of biotechnology likewise as the benefits, so decisions can exist made with as much information as possible. It's important to understand the risks so they tin be addressed."

Muir also cautions that the results of his laboratory study should be interpreted conservatively. "The study does confirm there are significant risks to natural animal populations associated with the release of transgenic animals. We assumed a consistent environment with but 1 variable – sexual preference for size coupled with low life expectancy for the transgenic. The natural globe is not nearly as orderly, and genetic background changes could negate the Trojan gene," he says.

The authorisation of sexual preference over Charles Darwin'southward classic theory of survival of the fittest is not unknown to wildlife specialists and geneticists. Muir likes to apply the example of the male bird of paradise with its long swells of gloriously colored plumage every bit an example: "The male bird of paradise with the longest, thickest tail attracts the most females. Subsequent offspring likewise exhibit the long tail and also compete well for females. Unfortunately, the birds with the biggest tails also have the biggest problem escaping predators who capeesh large birds pinned in identify by their plumage. Manifestly the bird with the virtually sex entreatment is the also the worst choice every bit a fit mate. Not different high schoolhouse, some might say."

The researchers' next goal is to replicate the study with larger fish of economical importance in a bigger environment. They're looking for an indoor pond puddle where they can raise tilapia and check the results of the medaka report.

Sources: Bill Muir, (765) 494-8032; bmuir@purdue.edu

Rick Howard, (765) 494-8136

Author: Chris Sigurdson, (765) 494-8396; sig@aes.purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu

NOTE TO JOURNALISTS: Copies of the journal article are available from Bill Muir, (765) 494-8032; bmuir@purdue.edu.

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Purdue animal scientist Bill Muir and colleagues hope to extend their inquiry on bioengineered fish to species that may exist used in fish farming, such as this tilapia. (Purdue Ag Communications Photo past Tom Campbell)

A publication-quality photograph is bachelor at the News Service Web site and at the ftp site. Photo ID: Muir.trojan

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Abstract
Possible ecological risks of transgenic organism release when transgenes affect mating success: Sexual selection and the Trojan cistron hypothesis William 1000. Muir and Richard D. Howard

Widespread involvement in producing transgenic organisms is balanced by concern over ecological hazards, such as species extinction if such organisms were to be released into nature. An ecological chance associated with the introduction of a transgenic organism is that the transgene, though rare, can spread in a natural population. An increase in transgene frequency is ofttimes causeless to be unlikely because transgenic organisms typically have some viability disadvantage. Reduced viability is assumed to be common considering transgenic individuals are best viewed as macromutants that lack any history of selection that could reduce negative fettle effects. Withal, these arguments ignore the potential advantageous effects of transgenes on some aspect of fettle such equally mating success. Here, nosotros examine the take chances to a natural population after release of a few transgenic individuals when the transgene trait simultaneously increases transgenic male mating success and lowers the viability of transgenic offspring. Nosotros obtained relevant life history information by using the pocket-sized cyprinodont fish, Japanese medaka (Oryzias latipes) as a model. Our deterministic equations predict that a transgene introduced into a natural population past a small number of transgenic fish will spread as a result of enhanced mating advantage, merely the reduced viability of offspring will cause eventual local extinction of both populations. Such risks should be evaluated with each new transgenic animal before release.

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