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Thursday, February 21, 2013

The truth about genetic engineering

Because genetic engineering is so often misunderstood, I'd like to explain what it is. Genetic engineering is simply a catch-all phrase for cultivation techniques that involve direct manipulation of genes. You can add a gene to an organism that didn’t previously have that gene or you can remove or alter an existing gene. Either way, you’re limited to genetic changes that will be viable in the resulting organism just as you would be by crossbreeding.

The following diagram compares conventional breeding to genetic engineering (transgenesis or cisgenesis). By the way, a ‘cultivar’ is a currently available version of the crop, and a ‘plasmid’ is a small circle of DNA that functions as a vehicle for transferring your gene of interest. Note that you have much less control over what gets added to the genome with conventional breeding. Also, ‘many backcrosses’ could mean hundreds of generations.

This brings me to some important points. The fact that the genes have been manipulated doesn’t automatically make the result toxic. It depends on which genes have been added or altered. If you add beta-carotene genes to rice, you get a crop that could potentially save hundreds of thousands of children from dying or going blind from vitamin A deficiency. 

Sometimes, genetic engineering even brings unexpected benefits. For example, John Haegele and Frederick Below from the University of Illinois found that Bt corn has much higher yields than conventional corn. Bt corn is corn that is genetically engineered to contain a gene from a soil bacterium named Bacillus thuringiensis (hence the ‘Bt’). The gene in question encodes a protein that is toxic when ingested by a specific type of insect pest. It is not toxic to other kinds of insects such as bees or beetles, and certainly not to humans or other vertebrates. Bt corn does, however, have far less predation from rootworms and consequently, the plants have a much healthier root system. This, in turn, allows the plants to take up nitrogen more efficiently, resulting in higher yields with less added fertilizer.

This is good news because genetic engineering is here to stay. As more and more genomes are being sequenced, it’s ridiculous to expect crop scientists to cross breed generation after generation hoping to get a desired trait when they can just add the gene they’re interested in. Perhaps more importantly, genetic engineering is increasingly being used in medicine. It’s used to develop strains of mice or other organisms that mimic human diseases, and to produce products such as insulin and human growth hormone. Obviously, I’m simplifying the work involved, but you get the idea. As a technique, genetic engineering is far too useful to give up.

Of course, there’s the possibility of purposefully or inadvertently adding harmful genes. But those are problems of misuse, not with the protocol itself. While there will undoubtedly be unanticipated problems, these problems can and should be managed responsibly. And just to be clear, ethical issues involving patents or business practices are not an indictment of the methodology behind genetic engineering.