Wednesday, October 10, 2012

Genetically Modified Salmon

Genetically Modified Salmon

Two years ago, there was a huge debate in the US about should the government approve and introduce the genetically modified (GM) salmons for people to eat (O’Neil & Kimbrell, 2011).

GM salmons are one of the major applications of genetic engineering. Scientists introduce a desired trait to the wild salmons by manipulating its genome using genetic engineering technique to introduce Chinook’s DNA to an Atlantic salmon. The DNA is manipulated by polymerase chain reaction (PCR).

PCR is a 3-step cycle. Billions of copies of specific segment can be quickly replicated in few hours. Desired RNA of Chinook salmon is chosen, isolated and amplified by PCR. First, the reaction mixture is heated to denature the DNA strands, then it is cooled down to allow hydrogen bonding of single-stranded short DNA primers complementary to sequences on the opposite strands at each end of the target sequence. At last, target sequences are extended by adding nucleotides with DNA polymerase in the 5’ to 3’ direction for extension. The reaction is possible because of the heat-stable Taq polymerase was discovered. Taq polymerase lives in hot springs so it can withstand the heat in the first step of the cycle.

Figure 1 Illustration of the Polymerase Chain Reaction (Reece et al., 2012)

The plasmid is then constructed with selectable marker gene, which contains the promoter and terminator. Transcription is initiated by the promoter region and terminated in the terminator region. The promoters allow GM salmons have the growth hormone that it normally would not and it allows them to grow twice the size than wild Atlanta salmons in a fast rate (Madin 2011). The Plasmid DNA with new genes can be inserted into bacterial cells and the bacteria will then express the genes.

Figure 2 Comparison of GM salmon and farm salmon (Thompson 2011)

There are lots of controversies on whether or not GM salmon is safe to consume. Up to date, there is no concrete evidence that it is harmful to human, as it is quite impossible to carry out controlled experiments due to our mixed diet (Thompson 2011). Another big concern is the environmental risks of wild salmons extinction. People feared that if they escaped to the natural environment, they might compete with the wild salmons for food and wild salmons would not survive as food source become more scarce. Also, there may be a change in the food chain due to change in prey some animals and eventually affect the whole ecosystem.

Though there are many controversies on GM salmons on food safety and risks to the environment. There would be lots of benefits if a stable food source can be created, for instance solving food crisis in third world countries. With more research and trials, scientists are trying to collect more experimental data to see what will occur to the genetics of GM salmons after breeding. Hopefully one day it can be proven that GM salmons pose no risk to human health and the nature.


1. Madin E., 2011. Genetically Engineered Salmon Pose Environmental Risks That Must Be Considered. [Online]

Available at:

[Accessed 9/10/2012]


2. O’neil C. & Kimbrell A., 2011, Biotechnology: US Congress right to halt GM salmon, Centre for Food Safety, Washington DC, 476: 283. [Online]

Available at:

[Accessed 8/10/2012]


3. Reece J., Meyers N., Urry L., Cain M., Wasserman S., Minorsky P., Jackson R., & Cooke B., 2012, Campbell Biology, 9th ed, Pearson Education, Australia [Book]

[Accessed 7/10/2012]



4. Thompson P., 2012. The GMO Salmon Struggle: FDA May for First Time Ever Approve Genetically Modified Animal for Human Consumption. [Online]Available at:
[Accessed 8/10/2012]

 s4283414 Jenny Tsang