John Ogunlela
Cattle owners dislike horned cows because they pose dangers to other cows and to the cattle handlers. As such, horned cattle attract pricing discounts in the market. The only way to make cattle hornless is to remove the horn buds in a rather brutal process while the animals are still very young.
There is this hornless (or, polled) cattle breed however, called the Angus, a beef animal. It is genetically pure for the polled condition and a genetics firm in named Recombinetics, working with researchers in the University of California-Davis decided that using the polledness gene in the Angus breed, it will make the most famous milk cattle breed, the Holstein hornless through gene replacement .
The researchers succeeded and their polled Holstein animals were born looking quite healthy. The news went round the animal industry quickly even as careful researchers demanded caution and requested further observations to make sure these animals had not been genetically altered in other ways that could make them dangerous for human consumption or to the bovine genome in general. “To me, this is precision breeding as much as anything,” says Alison Van Eenennaam, an animal geneticist at University of California-Davis who led the research. “We’re able to introduce a desired genetic variant [into Holsteins] very precisely, without affecting any of the other genetics that makes them great milk-producing animals.”
It turns out he’s wrong about that. In July this year, scientists in the Food and Drug Administration’s (FDA) Center for Veterinary Medicine found that Recombinetics’ polled cattle had some notable irregularities.
During a routine data run, they unexpectedly found foreign, non-bovine DNA that had bound itself to the animal’s genetic sequence during the edits—specifically, genes from the lab material. And while no one’s saying that the mutation is unsafe, either to humans or animals, no one can guarantee its safety either. It’s casting the slam-dunk claims about gene editing in doubt, and animal scientists are calling to pause the rush to food of the future. In any case, everyone was afraid of consuming these animals and they were killed and cremated.
There have been successfully engineered organisms however, and a good example is the ‘Aquabounty’ Salmon. The fish was engineered to grow twice as fast by incorporating genetic materials from another strain of salmons and an eel. The experiment was successful and the product has been cleared by regulatory authorities – not without serious debates – for consumption in Canada in 2016 and the United States this year.
In 2015, a team of researchers at the University of Missouri used similar methods to breed pigs that are resistant to the Porcine Reproductive and Respiratory System (PRRS) virus, a disease that causes about 600 million dollar losses to the pork industry globally every year. The pig genome was modified to eliminate the site where the disease-causing virus binds. If the virus cannot bind on the particular site on the gene sequence, it loses its ability to cause a disease.
Exactly a year ago, the same Missouri team announced they’d produced a litter of pigs that are genetically resistant to an intestinal disease called Transmissible Gastroenteritis Virus, or TGEV. No side effects have been observed in the salmons and the pigs described above and they remain GMOs that are beneficial to humans. Foods apart, humans have been genetically modified too – by the Chinese – and the product are twin girls who are forever immune to a major strain of HIV that causes AIDS.
All living things are made by nature’s coding entities called genes, which themselves are chains of deoxyribonucleic acid or DNA. The DNA consists of three parts, two of which are essentially fixed but the third part is changeable with four (or five, in the case of the ribonucleic acids, RNA where Guanine is replaced by Uracil). These changes are represented by letters denoting the chemicals and each sequence of three of them forms a distinct genetic code called a codon. Each codon is a life-altering triad that firmly decide how the organism is going to be built and what is to follow what in that building process. In genetic engineering, scientists go into this sequence or chains of codes to identify what is coding for what and how those code chains can be terminated or replaced or both.
When chains of codes are terminated and nothing further is done, the cell is capable – and is going to – repair itself by sealing up that genetic break. In some gene editing cases, this is all that is done and no foreign gene sequence is brought in. In other instances, the chain of codes is cut and a preferred code is dragged into that site to replace the snipped code as was the case with the polled cattle.
The code for the hornless condition was picked from the Angus breed and inserted into the site in the Holstein zygote where there used to be a gene for growing horns. Things went wrong however because the reagent plasmid itself got caught up in the works and became a part of the new, engineered animals. Unfortunately, the reagent caused a condition that made antibiotics of no effect on bacteria in the gut of the new animals. In a third instance, genes are brought in from a completely different organism to replace the cut ones. These are the major classifications of genetic editing works and they are called Site Directed Nucleases (SDN) 1,2 and 3, as described above. The scissors used in cutting genes are not what your eyes can see. They are chemical reagents called nucleases and they have abilities to focus on particular sites on a gene and this is the reason their actions are called site directed actions.
In Australia, the government realised one of the reasons its dairy industry was falling behind that of New Zealand and the United States was because those others feed their animals with grasses that yield better nutrition (in terms of dry matter). Australian authorities do not allow the use of genetically modified crops and animals but in this case, it authorized the genetic engineering of the rye grass, a popular cattle fodder in the country so that it can yield more and thus reduce the cost of feeding cattle in the country. Strictly, the SDN -1 was authorised as it is considered close to natural mutation and bearing the least risk of something going out of hand.
So, are genetically modified foods safe for human (and animal) consumption or not? The answer is, nobody really knows for sure but fears consequences are valid and the need for caution are founded. The risks however remain a potential rather than actual even in truly transgenic SDN-3 organisms.
The incorporated foreign gene could gradually, through some fortuitous chemical or genetic processes become active in ways not anticipated and become noxious. For now however, regulators are on the brakes with respect to GM crops but their grip is, well, slackening and that trend is expected to continue. If our fears are realized, GM crops will lead to diseases that are resistant to the drugs we know and to physiological reactions that we are totally unprepared for. New diseases can emerge and our entire digestive system can be altered through the actions of new microbes that have altered the biotic and chemical balance in our guts. All the same, knowledge must advance and with the emergence of more effective gene editing tools (for example, the CRISPR – clustered regularly interspersed short palindromic repeats), there will be rapid progress in engineering crops for human use.
Already, grasses have been engineered to appear greener and fish to grow faster. We can only watch out for more.
–Ogunlela wrote in from Osun State
