Normally, an extra pair of chromosomes would be considered dangerous. But what if we could design our own? According to biologists, we could create custom-built chromosomes to fix a variety of health problems, and even give us new abilities. Here’s how a 24th pair of chromosomes could change our biologies forever.
To learn more about this incredible prospect, we spoke to biophysicist Gregory Stock. He is the Chief Science Officer of Ecoeos, a company that develops clinically-validated DNA tests to measure personal susceptibility to environmental toxins. Stock is also the author of Redesigning Humans: Choosing Our Genes, Changing Our Future, and the recently updated Book of Questions which is scheduled for release later this year.
But before we get into artificial human chromosomes (AHCs), let’s quickly review what chromosomes are in the first place.
Chromosomes are packages of the genetic material located in our cells — the foundation of our basic biology as an organism. They’re not a recipe for us, but they do specify the sequence of events that lead to the development of mature organisms. Chromosomes offer a way for nuclear material to be packaged, protected, and maintained as it’s passed from cell to cell.
Different components of chromosomes are turned on and off in different contexts and in various parts of the body. There are anywhere from around 250 million bases on some chromosomes, down to about 50 million on others.
We humans have 23 pairs, for a total of 46. These structures are very tightly organized windings of DNA that become encoiled in a complicated way and allow for division each time a cell divides, so that each cell has the same complement of genetics.
There are two types: autosomal and sex chromosomes.
Sometimes, an added chromosome can be problematic. An extra chromosome 21 leads to trisomy, also known as Down syndrome. XXYY syndrome happens when males have an extra X and Y chromosome, leading to developmental delays, extra height, and learning disabilities.
But adding extra chromosomes artificially won’t necessarily be a bad thing. And in fact, they could be quite advantageous. When inserted during the in vitro fertilization (IVF) stage, they could serve as remarkable and flexible platform for the insertion of genetics.
“The main attraction of creating an artificial human chromosome is that they can be passed down from generation to generation,” says Stock. “There’s all sorts of mechanisms and structures in place that would allow for the division and faithful reproduction of those chromosomes.”
What’s more, he explains, physicians will be able to control the various elements of the genetic sequences. We’ll be able to turn them on or off, or even accelerate their expression. Certain chromosomes may be put in place to serve as a backup, or to function at a specific stage of a person’s life (such as during elderly years when existing genetics isn’t up to the task).
Stock says we could add an additional pair, bumping our total up to 24. Or, if we wanted to deploy them in discrete and tidy packages — which would contribute greatly to their flexibility — we could just keep adding pair after pair after pair. In fact, the technology to do this could come sooner rather than later, with chromosomes containing a mere 10 to 20 megabases.
“Ideally, if you were to create an extra chromosome, rather than putting extra genetic material and inserting it into an existing chromosome — where it might be put into a random spot or put into something else that’s going on — you have a very controlled environment,” he told io9. “You can create these things, duplicate them independently, and put them in different organisms. It’s a very controlled process.”
And in fact, this is already being done. The prospect got off the ground back in 1997 after John Harrington and Huntington Willard developed a technique for doing so. Bacterial artificial chromosomes are used in labs all the time, as are yeast ACs (called YACs). Biologists have even created ACs in mice. We’re currently at the nascent stage of human artificial chromosomes.
“When you start to think about the potential for architectural intervention in humans, an attractive feature is that it could be so controlled that you could make it conditional,” says Stock. “This way, you can turn the elements on or off and at different points — similar to the way it happens in the fine orchestration of genetic activity in the developmental process.”
Stock says that we’ll be able to put some new genetic material into a chromosome and not have to turn it on until the individual is an adult. As a result, we won’t be tampering with the very sensitive arena of human development — something that would prove to be far more difficult to manage in a fully mature adult.
He envisions the day when we’ll be able to use AHCs to increase human immune function, slow down the effects of aging — or even boost our memory and intelligence. They could serve a new form of immunization, protecting against specific diseases like AIDS or certain cancers.
AHCs could also give humans new capacities altogether. Stock speculates about a range of futuristic enhancements, including the ability to see ultraviolet light, or navigation in the dark by a system of sonar similar to that employed by bats.
I asked Dr. Stock if this could be considered a therapy or an enhancement.
“Well, I’d call this a therapeutic enhancement,” he replied. “But ultimately it’s a matter of perspective.”
Indeed, some people might consider a super-juiced immune system that's triggered later in life as an enhancement. Same for chromosomal interventions that could extend a person’s lifespan. Others, on the other hand, might simply say it's just a different way of doing therapy.
“But it also depends on whether or not someone is on the lower or upper area of performance of a specific category,” he added. “If you have diminished function, then they’re likely to be considered enhancements.”
One important thing to remember about enhancement, says Stock, is that it’s going to be tough. Unlike the repairing of health problems, which tend to be simpler, enhancement will elevate performance, which could result in unintended and unforeseen consequences. “That will require us to get everything right,” he says.
Stock points to the controversial realm of IQ and cognitive enhancement.
If somebody is functioning with an IQ of 70 — which is a couple of standard deviations below average — that may be the result of some very specific developmental problems that occurred, or some other underlying issue that’s relatively easy to repair. That person, if it’s caught early enough, might end up having an average IQ — which would most certainly seem like an enhancement to them.
But if a person has an IQ of 160, which is way out in terms of normal function, we’d be hard pressed to enhance their performance without having some subtle, or not so subtle secondary consequences that would be very difficult to gauge.
“For example, super-bright people often have quirks in their personality that, depending on your viewpoint, is either a positive a negative,” adds Stock.
Stock says that the limited enthusiasm behind AHCs is due to a number of other viable interventions that could basically do the same thing.
“Naturally, we’re going to do what’s the safest and most effective thing.”
He points to embryonic genetic screening and drug treatments. Or even using assistive devices, like mobile phones, to ‘enhance’ our memories.
“All our tight associations with technology make us functional cyborgs, in which case we’re really and truly enhancing ourselves — so there are only a very few applications in which there aren’t easier paths when compared to genetic enhancement.”
Stock also notes the potential for somatic engineering, in which the existing cells of adults can be modified by injecting short genetic sequences.
“But technologically it’s much easier in the embryo,” he says. “With artificial human chromosomes, they’re automatically present in every cell in the body, and it can be set up in ways in which it can be turned on and off locally, like taking a specific drug that triggers it.”
This is a very important issue, he adds, because it makes the entire system failsafe.
I asked Stock about the ethical concerns related to the potentially permanent modification of the human germ line.
“Yeah, the general tone of the discussion is, ‘How could you possibly do that!? You’re altering our genetic heritage, and you’re altering genetics in humans — because once you get into our genetics then it’ll be passed on to the next generation!’”
But Stock thinks this represents a fairly limited view of technology.
“The fear that future generations won’t be able to remove it, inactivate it, make it non-heritable, or replace it with something better seems to me to be a rather tortured scenario,” he says.
But looking at advanced technologies, and then representing the context of them as being stationary and very limited, doesn’t make a lot of sense to Stock. What’s more, these technologies will be tested in animal subjects. And in fact, an artificial human chromosome has already been injected in mice.
“My suspicion is that we wouldn’t be reproducing naturally once we’re in that state,” says Stock, “because there’s so much more that we’ll be able to do 25 years from now. And we’re definitely going to want the next generation of artificial chromosomes. These things tend to move very quickly.”
As for a timetable, Stock expects to see the first artificial human chromosome put to use in about a generation from now, perhaps in 20 years.
“Bioengineers tend to underestimate the complexity of human biology,” he says. “These developments often come at a slower pace than we imagine. But they’re inexorable.”
Image: Creations/Shutterstock; Alila Medical Images/Shutterstock; Tehelka.