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

Wednesday, March 28, 2012

Genetics of body shape: Apple or Pear?

Genetics of body shape: Apple or Pear?

New recent scientific study discovered that genetics play a significant role in body fat distribution and determines whether your body shape is “apple” or “pear”. These genetic variants have different health implications dependent on the fruit-based analogies of body shape. Moreover, it was found that a genetic variation relevant to fat distribution has much stronger effects in women than in men.

An international team of scientists, led by the Medical Research Council and Oxford University identified the biological processes that are associated with fat distribution and obesity.

Figure 1 Waist-to-hip ratio and a nucleotide polymorphisms

They discovered that DNA variations could be connected to waist-to-hip ratios. They found 13 single nucleotide polymorphisms associated with body fat distribution. These DNA regions are involved in regulating cholesterol, triglyceride levels and insulin.

Figure 2 Body mass index (Phoenix evolution)

Moreover, they investigated the genes that have correlation with Body mass index. BMI is a measure commonly used to classify adults. BMI of 25 to 30 is accepted to be overweight and a BMI of 30 or higher is known to be obese. From this research, 18 new genetic regions that are associated with increased susceptibility to obesity were discovered.

Also, a studied investigation has proven a trend that those who inherit a larger amount of BMI-increasing genes from their parents have weights 7-9kg more than those who don’t inherit as much of these genes. This variation in weight is entirely the causation of different genes different people have.

Figure 3 Apple shape vs. pear shape

These genetic variants have different health implications by looking at the body shape fruit-based analogies to describe body shape. For those who don’t know yet, “apples” tend to carry more weight around their waist whereas “pears” tend to be heavier around the hips and thighs.

Unfortunately, for the apples, their susceptibility to accumulate excess fat around the waist region puts them at a greater risk of causing a type of heart disease and type 2-diabetes. On the other hand, “pears” thought to be offering some protection against high blood pressure and diabetes.

Figure 4 Distribution of fat in males and females

The results from the research state that there is dissimilarity in fat distribution between the sexes. It is because, 12 of 14 SNPs are associated with body fat distribution whereas there are only three of 14 SNPs in men.

Where the body fat lies in the body is a crucial role in causing diseases. A better and improved understanding of the risks that genetic facture underlying increase waist and hip size may aid in allowing for quicker remedies and therapies.


Medical Research Council - News - Apple or pear? New insights into the genetics of body shape. 2012. Medical Research Council - News - Apple or pear? New insights into the genetics of body shape. [ONLINE] Available at: [Accessed 21 March 2012].

Press Release - 23andMe Presents Top Ten Most Interesting Genetic Findings of 2010 - 23andMe. 2012. Press Release - 23andMe Presents Top Ten Most Interesting Genetic Findings of 2010 - 23andMe. [ONLINE] Available at: [Accessed 21 March 2012].

European Journal of Human Genetics - Genome-wide analysis of epistasis in body mass index using multiple human populations. 2012. European Journal of Human Genetics - Genome-wide analysis of epistasis in body mass index using multiple human populations. [ONLINE] Available at: [Accessed 21 March 2012].