Nature’s operating system is the genetic code. At its simplest the code is made up of 64, three letter words called codons. This is the language our genes are written in.

Viruses are able to infect our cells and make us sick because they use the same operating system. Basically a virus enters a cell and gives it a series of commands via the genetic code to make new viruses.

If we engineer our cells to speak a different language, then the viral instructions will be meaningless. Our cell will ignore the virus and eventually clear it out of our system.

Re-engineering a code that has been around for a billion years might sound hard, but one of its properties makes it doable. Many of those 64 words mean pretty much the same thing. Our genetic code has a lot of synonyms.

A simple code with lots of synonyms makes re-engineering our operating system relatively simple.

The idea would be to change the meaning of a few of the synonyms. What we’d do is pick a codon, maybe TAG, and change all of the TAGs in our genes to its synonyms, TGA and TAA. Then we’d make TAG code for something else.

Now when a virus enters the cell, its instructions to the cell are gibberish. Whenever it gives cells an instruction with TAG somewhere in it, the cell misreads it and so can’t do as it is told. The cell can then calmly ignore the virus and go about its business. (Click here to learn more about the science behind this.)

Making the resistance more or less permanent requires changing more than one synonym. Viruses are small and mutate like crazy so we have to make it so the virus requires at least ten and probably many more simultaneous mutations to become resistant. The only way to do this is if we make all the changes in one fell swoop.

This all sounds like some Hollywood "B movie" but scientists are very close to testing this theory out in E. coli, a common lab bacterium. Scientists have made the appropriate changes and are stitching together the DNA as we speak. Soon we should know if this strain of E. coli is immune to the phages that plague it. (Phages are what viruses that attack bacteria are called.)

If this works in bacteria, then it might work in people too. But it isn’t a for sure thing. We are more complicated than a bacterium and the genetic code is more complicated than it first appears.

A big challenge that has important implications is that we can’t make the necessary changes a bit at a time. If we do that, viruses will mutate along with us and keep up. We need to make all the tens of thousands of changes all at once. This is where the trouble can start.

Technical Risks

There are at least two sets of technical risks associated with doing something like this. The first just has to do with how often we make a mistake while changing tens of thousands of our DNA letters. No matter how good we get, there will always be a chance that we make a mistake. And since these changes are in genes, some of the mistakes could be really bad for our health. I am not sure we can ever be careful enough to not introduce a few errors here and there.

The second big risk is that we do not fully understand how our DNA works. What if there are very small genes we don’t know about that use the synonym that we have changed? The consequences could be severe if that “genelet” plays an important role in the cell.

Another problem in that the synonyms may not be as alike as we think. We’ve known for a while that not all synonymous codons are created equal. For example, sometimes when we try to optimize a gene by selecting what we think are better codons, the gene stops working.

We are bound to make a few mistakes when making so many changes to our DNA.

A study just out in yeast confirms that some of the specific codons in a gene are there for a reason—not all synonymous codons are used in the same way in the cell. It looks like some words are preferred at certain parts of a gene.

This means we may not be able to simply swap one codon out for another in a gene. And since all the genes are competing for a limited amount of machinery using specific codons, we don’t really know what effect eliminating all these codons will have on all 20,000 or 25,000 of our genes. We may slow things down as the parts of the cell all compete for these limited resources.

What makes each of these problems worse is that we will need to make all the changes at once in a cell to keep viruses from catching up to us. We will be able to test a lot beforehand, but it may not be enough. We may miss something and that would be unacceptable here.

Remember, we are talking about people here not bacteria, yeast or daisies. Mistakes mean a dead baby or one with disabilities. I am not sure there will ever be enough testing to make this safe enough to be worthwhile.

Implementation Risks

As you’ve seen, there are definitely health risks associated with doing this (I’m sure I haven’t thought of them all). But the ethical risks might be worse.

These changes can’t be made in any of us alive today. They would have to be made by inserting the changed DNA into a stem cell and coaxing that stem cell into becoming an embryo. This means that instead of changing the current human race, we’d be creating a new one.

An immediate problem is how we choose who gets to be virus-resistant. And scarily still, whose DNA gets to live on. So the first step will be figuring out who gets to have virus-free children and how we “choose” what DNA that child will have.

One way would be to make it so everyone who wants a child gets the option of having the child be virus-resistant. Maybe parents fertilize an egg the old fashioned way, the embryo’s DNA is sequenced and the DNA made matches this embryo’s. This makes me a little squeamish and is a strange gray area. We have eliminated the embryo but essentially cloned it…is the child truly identical?

This sort of re-engineering might result in two species of humans that cannot interbreed. Yikes.

Another option would be to use a computer to generate a mix of the parents’ DNA and then to make that DNA and grow it into a child. This is scary as you know people will be tempted to choose the DNA rather than letting it come down to chance. We’ll definitely end up with a very different human race in the end.

Both of these would be pretty expensive dollar-wise but are better than an option where a chosen few get to have virus-free kids. How would that decision be made and who gets to make it? (Hint: The poor would be poorly represented.)

Whatever option we choose, there will still be another key issue. Engineered humans and natural humans won’t be able to have kids together. This opens up a whole can of worms if the two groups are around together for any length of time. And chances are they will (unless we outlaw having kids the old fashioned way). We will have artificially speciated the human race!

There is no way that comes out well. Most likely we’ll split into a group of haves and have nots decided by genetics. The engineered humans will have kids together and the natural humans will too. Occasionally a natural human could make enough money to have an engineered child but for the most part they’d be separated. I’ll let you paint that dystopic future in your head!

These are a few of the ethical dilemmas I can think of off the top of my head. I am sure there are many more.

This may all seem like a problem for Captain Kirk, but it is closer than you might think. It is really important to start talking about this stuff now so we can think out how we are going to deal with these sorts of decisions in coming decades. Before we know it, the need to decide will be upon us.

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