Suppose we managed to find a way to change the DNA in every cell of our body, perhaps by artificial virus or something like that. What would happen if we made such a change, for instance changing blue eye color to brown? What about replacing all the DNA with that from a monkey, or a dragonfly, or even a plant? I’m thinking in the first case, eye color would either change or it wouldn’t, and in the other cases, we’d either change to that organism or die. So what would actually happen? What are the extremes?
I assume here you are only speaking of changing one gene. Many genes are only turned on at certain stages in development. I am not sure how often cells in the iris are renewed; it may be that changing the gene after adulthood could have little or no effect.
In the second case your physiological processes would be thrown out of whack so severely that you would promptly die. You might survive for a while with the DNA of a closely related animal such as a chimp, but even in that case there would soon be some ill effects.
You would not change into the other organism because, as I said, many genes are activated only at certain stages of development. You cannot develop into a dragonfly if your starting point is the body of an adult human. You can only develop into a dragonfly if your starting point is a dragonfly egg.
Well that makes sense. So there are only a few things you could change that would have the desired effect, namely small individual changes that are frequently being read from DNA.
One more extreme situation. What would happen if your DNA was swapped with that of a single-celled organism, such as a bacterium? Sure you would cease to exist as a human being, but would your body be replaced with a shitload of bacteria?
No; bacteria have a very different, and much less complicated, type of cell structure from humans. Bacterial DNA would be unable to work the cellular machinery of a human-type cell (or of anything from an amoeba on up).
Even if you replaced the DNA with that of an amoeba, which at least has a similar cell structure, it wouldn’t work. For one thing, many human cells cannot survive in isolation but instead depend on support from other cells. Also, I think the metabolic differences would be too great for amoeba DNA to be able to “run” a human cell.
Interesting. I figured changing the DNA would make the cell morph fairly quickly. Maybe not. It looks like I’ll never have a chance to be a Venus flytrap after all.
Body cell types depend not just on their DNA but on the developmental processes they and their ancestral cells went through. All the cells of your body have the same DNA, but they are of vastly different kinds: bone cells, muscle cells, nerve cells, and so on. Many of the genes in a particular cell type are “shut down” and inactive. Even your own cells, with the same DNA, usually can’t switch between types.
If you got Venus fly-trap DNA, how would it know which of your cell types to convert to leaf cells, which to stalk cells, which to root cells, which to flower petals, etc?