Genetic modification of animals has been taking place since the first domestication of animals around 12000 years ago (whether unknowingly or not) when people bred animals that displayed desired traits with others that had the same traits which resulted in offspring that had these characteristics. In more recent years this modification has become a lot more direct and more useful than just producing the biggest crops.
The enviropig is a genetically modified organism, meaning it contains foreign DNA. The enviropigs were developed in order to allow pigs to digest phosphorus. To insert the DNA, restriction enzymes are used to break the DNA at specific sites using markers. These restriction enzymes have been found in bacteria cells. The enviropig has two foreign genes inserted into it, these genes are found in mice and code for the digestion of phosphorus. In animals the foreign DNA is then inserted into the pronuclei. Pronuclei are formed in the early stages of fertilization, just after the sperm has penetrated the egg (Morris 1995, p.52). At this time the male and female DNA still have separate nuclei (pronuclei) which slowly move and fuse together. The foreign DNA is inserted into these pronuclei using a microinjection. Once the DNA is inserted scientists use a ligase to join the DNA fragments together. The ligase works by reclosing the phosphorous backbone of the DNA . There are two different types of ligase; one is found in bacteria cells and the other in eukaryotes. If the DNA is correctly inserted into the new cell it then becomes part of the chromosomes and is passed onto future generations like a normal gene would be.
As normal pigs can not absorb much phosphorus it is passed out in their waste. The run off from this waste contains high levels of phytate phosphorous, when this reaches the water ways it leads to widespread plant and algae growth. The increased algae and plant growth taints the water while also reducing oxygen. The reduced oxygen level then kills off fish and many other aquatic organisms that play indispensible rolls in the food chain. This has a devastating impact on the environment and is ranked as one of the most serious environmental problems that we are currently facing. The enviropig could do away with this problem as enviropigs excrete as much as 60% less phosphorus than normal pigs. Meaning this technology has the ability to help solve world wide environmental problems that previously would have gone on unaided. Sadly however in Australia it is still illegal to modify pigs –or any other organism- in such a way.
Original Article: Forsberg, Cecil & Phillips, John n.d, Guelph Transgenic Pig Research Program, viewed 30 March 2009
