By Robert Hazen, George Mason University
Some people are troubled by the unintended consequences of introducing what they see as essentially new species, or new varieties of life, into stable ecosystems. If we introduce a plant that’s resistant to insects, is that going to change the natural balance of an ecosystem? On the other hand, nature is constantly introducing new varieties through natural processes, through mutations and so forth.
Genetic Engineering of Animals
We know that complex systems, like ecosystems, may be changed in dramatic and unexpected ways, just by introducing small changes. We have to ask ourselves, is there a real difference between what nature does, and what humans engineer? It’s a real philosophical question. However, the most troubling questions arise in the context of the genetic engineering of human beings.
Here we see the greatest opportunities and the greatest risks at the same time—altering animals, including ourselves.
Genetic engineering of animals is extremely difficult, because we haven’t yet learned to duplicate animals from the genetic material of a single cell. In contrast to bacteria and plants, which can often be modified by brute-force, and then regrown from a single cell that’s been modified, we can’t really clone animals easily from just any single cell.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
Jurassic Park
Some of the difficulties associated with genetic engineering were captured in Michael Crichton’s Jurassic Park, which dealt with bringing back the dinosaurs. It’s a fascinating story, the idea that we can start with dinosaurs at the smallest scale, the scale of a single cell.
The conceit of this novel is that we find ancient amber that preserves insects, like bloodsucking mosquitoes. If we can then go into the mosquito’s gut and actually pull out some of the blood cells that it’s been sucking, we actually would be able to, perhaps, recover a complete set of DNA from a dinosaur.
Dinosaur DNA or Not?
It’s a fascinating idea, that we could somehow grow dinosaurs from this ancient DNA, but it’s not so easy. Each step in the Jurassic Park scenario does have a tenuous basis of fact. We certainly do have fossil insects beautifully preserved in amber, but they don’t contain pristine dinosaur blood cells. In fact, it’s hard to get even a trace of ancient insect DNA, which is going to be much more common in an insect than the dinosaur DNA.
We have a few scientists who have reported the extraction of ancient DNA from samples of well-preserved dinosaur bones, but these are invariably broken into tiny fragments of only a few base pairs long, at most—if indeed they’re dinosaur DNA, and not later microbes that have fed on the dinosaur bones.
Bringing Back Ancient Life Forms
The most basic problem in bringing back any ancient life form is obtaining the complete genome: how do we get a complete set of chromosomes? For DNA to work properly, every base pair has to be in line, on the complete sequence, and we have to have the complete set of chromosomes.
The reality is that DNA tends to degrade over time; we just can’t preserve a genome for millions of years. It is disturbed by heat, radiation, carbon-14, and the DNA starts degrading, and that’s an irreversible process. This is also true for DNA in our body, which suffers thousands of hits every day, in every cell; but the living body has many different repair mechanisms. It continuously reverses this damage in every cell of our body. As soon as the organism dies, the repair mechanisms stop, but the damage goes on.
Let’s say that the unlikely event happens, and we can obtain a complete dinosaur set of chromosomes. It might even be possible to insert those chromosomes into a modern egg, but we don’t have any idea how to trigger or sustain the development of those chromosomes—of that first fertilized cell, and sustain that growth into a dinosaur. The growth of an embryo is an incredibly complex process. It’s governed, at least in the early stage, by the chemical signals from the egg itself, from the environment in which the DNA finds itself. Consequently, the engineering of an authentic, living dinosaur is not a realistic goal, at least for the foreseeable future.
Preserving and Increasing Earth’s Biodiversity
More realistically, these techniques might be used to preserve or even increase Earth’s biodiversity. It might be possible, for example, to obtain an intact genome from a fossil mastodon, or a mammoth, which are relatively close relatives of elephants; many of these creatures are found preserved, frozen in the ice, in Siberian wilderness. They were captured in the ice, and were frozen, perhaps 5,000 or 10,000 years ago, so they haven’t had as much time to undergo damage; and they’ve been frozen, after all, which certainly slows down that damage process.
These remains provide trillions of cells to work with, and by combining all those cells, we may be able to extract intact chromosomes, or at least complete genomes, in one way or another. Perhaps, then, insert those chromosomes into an elephant, whose gestation period might be comparable to that of a mastodon or a mammoth, and we might even be able to reproduce these animals.
Even more realistically, we might be able to preserve libraries of genetic material for organisms now threatened with extinction—whales, condors, tigers, many endangered rainforest species. We can preserve them in the form of a few cells, each with a complete copy of the unique genome. Then maybe, someday, we’d be able to figure out what to do with those genomes to bring those creatures back, if they do go extinct.
Common Questions about Genetic Engineering
The genetic engineering of animals is extremely difficult because we haven’t yet learned to duplicate animals from the genetic material of a single cell, unlike bacteria and plants, which can often be modified by brute force, and then regrown from a single cell that’s been modified.
The most basic problem in bringing back any ancient life form is obtaining the complete genome. For DNA to work properly, every base pair has to be in line, on the complete sequence, and we have to have the complete set of chromosomes.
The basis of the novel Jurassic Park is that if we find ancient amber that preserves insects, like bloodsucking mosquitoes, and if we can then go into the mosquito’s gut and actually pull out some of the blood cells that it’s been sucking, we actually would be able to recover a complete set of DNA from a dinosaur.
