From hand transplants to face transplants — including some really cool developments in whole-eye transplants — we're close to being able to put a whole new body together [source: UCSD]. (We're even so bold as to do cosmetic transplants to get a thicker head of hair [source: Lickstein].) But just because we're going big doesn't mean we have it all figured out; working on a much smaller scale is no less challenging (and maybe even more so). How will we ever be able to transplant some of our tiniest parts?
In some sense, the answer is that we're already quite adept at transplanting DNA. In fact, it's fair to say that for many of the organ transplants we do, we're effectively introducing donor DNA into the host. Even a simple blood transfusion is going to present new DNA into the host for as long as a few days [source: Gong]. Or take a look at bone marrow transplants. Bone marrow contains stem cells that control blood production. The stem cells in the marrow make new blood, meaning that transplanted bone marrow is making the blood for a host's body. The donor's DNA is going to be in all the new blood — permanently [source: Alizadeh].
Let's look at one more example of a place we're already "transplanting" DNA. Mitochondria provide energy to cells, and they have a different DNA than the one we typically think of. (You know, the DNA that tells us if we're going to have black hair or long eyelashes.) Mitochondrial DNA is matrilineal, meaning that it's passed straight from the mother. Defective mitochondrial DNA can be devastating; it can cause almost immediate death at birth or a drawn-out illness that ravages the body.
Scientists have now figured out a way to replace a mother's defective DNA with healthy mitochondrial DNA. It's pretty impressive. Nuclear DNA is pulled from the embryo and then transplanted into another embryo with the DNA from a healthy mitochondrial host. The rest of the host's DNA is removed, leaving the DNA from the mother, the father — and the healthy mitochondrial DNA of the host [source: Stein]. Britain is experimenting with the process, and — while no embryo has yet been transferred to a mother — the scientists are waiting on government approval.
Of course, this is one step beyond just transplanting DNA. It's combining three different DNAs in one recipient. But rest assured that DNA transplants are happening, on a smaller scale, with many organ transplants.