is it possible to alter the entire gentic code of a fully developed organism?

Question

perhaps via a virus or stem cell therapy. also to be specific, when i say alter i mean not only manipulate preexisting genes (turning them on or off), but adding or subtracting new genes. (also permenant, not temporary)

Answer 1

It's not only possible, it happens all the time.

This is what a retrovirus (like HIV) does. It infects a cell, forces it to add its genetic code to the host's, and then that DNA remains there FOREVER. This is why retroviral diseases are - for the time being - treatable but completely incurable.

Scientists have followed the virus' lead and done some similar things by replacing bad viral DNA with other things they want to give to the host creature. They have even treated human patients in this way by permanently modifying their DNA. But as a medical treatment right now it has a few problems.

The first is that they can't target where in the genome the DNA will end up. A virus will just cram the stuff in anywhere it can. This can be bad if the new section of DNA ends up interrupting some other important DNA sequence your cell was already using it. Retroviral therapy thus is a pretty good way to damage cells and give people cancer right now.

The second big problem is that your body can't tell a 'good' virus from a 'bad' one. It will fight off such treatment and try to prevent cells from being infected. As such, it's really hard to make sure EVERY cell in a body, or even in one tissue, is modified in this way.

Still, for some treatments this isn't entirely necessary. The trials I referred to above involved getting breast cancer patients' cells to produce their own medicine. Retroviral therapy is also being looked at as a treatment for diabetes.

If we solve the problems mentioned above, however, we could potentially use it to alter the DNA of even an adult in whatever manner we liked. Exciting!