A flaw very often pointed out in your run of the mill genetic terror story is the instant effect of genetic changes.

What would it take for a specific change in the specimen to actually appear (near) instantly?


I (well not really me, you know right) want to engineer a human individual to grow an additional finger.

  • Assume perfect knowledge required to engineer the required genetic code.
  • Injection vector etc. is all sorted out.
  • Assume high-tech tissue regeneration technology, which could regenerate limbs, but not a complete brain.

My genetic information is now within the specimen. From my (simple) understanding I have now changed the blueprint, the building plan for this individual, right?

  • Do I have to, say chop the hand off, and let it regrow, according to the new genetic code?
  • Will it grow itself somehow?
  • Can this change only occur in the next generation (offspring) and how to avoid this.

EDIT: This is not about changing the code itself, its about making the changes actually appear

FURTHER CLARIFICATION: Assume an advanced intelligence injecting precise dna snippets into humans. This is my major handwave.
Now I want to reduce -if at all possible- the following handwaves as much as possible, namely the circumstances under with the introduced changes would actually show themselves.

I changed from science-based to reality-check because the answer requires handwaves in its pre-condition.

  • 3
    $\begingroup$ Genetics = ultra complicated. See: xkcd.com/1605 . The short answer is: We don't know. Do you absolutely have to do this via genetic manipulation? $\endgroup$
    – Raditz_35
    Commented Jun 21, 2018 at 11:21
  • $\begingroup$ you're asking about giving superpowers via genetic modification? Okay. First of all, assuming the modification worked, the very first kid born with this mutation can make use of it, whatever it will be. Already a human with perfect night vision, amplified hearing and sharper sense of smell and denser tissue and harder bones would make for one heck of soldier for a special force elite or for a SWAT cop. Another mutation useful would be a glow-in-the dark rescuer. fire-resistant for a fireman...you name it $\endgroup$ Commented Jun 21, 2018 at 11:29
  • 2
    $\begingroup$ What would you consider instant? The finger growing in a matter of months would be considered really fast on a biological stand-point, if you want it to grow in a matter of minutes, then you will need magic. $\endgroup$
    – Sasha
    Commented Jun 21, 2018 at 11:30
  • $\begingroup$ All that organic tissue comes from something. Our bodies are the product of many long years of processing nutrients that our bodies receive through digestion or in the womb. From a physics standpoint, you're either destroying organic tissue elsewhere or you've just eaten an entire roast beef. $\endgroup$
    – Neil
    Commented Jun 21, 2018 at 12:06
  • $\begingroup$ It seems that you have already answered your own question with your initial 3 bullet points. I already wrote an answer, but rereading the question I wonder what there actually is left to answer. $\endgroup$
    – user3106
    Commented Jun 21, 2018 at 12:07

3 Answers 3


We don't know. There is no solution without a lot of handwaving or magic

There is no known scientific way to achieve precise results through genetic modification in more complex life like humans (unlike bacteria, etc.).
We have no idea what we would have to change for even regular things. Like making somebody have a tendency to grow bigger, stronger bones. Even without superpowers.

Genetic research has come pretty far since it began. And it helped significantly in the development of vaccines, understanding of cancer, immune system capabilities, but it is still very far from genetically engineering "higher-order" traits in animals (including humans).

If it was possible or even understood we wouldn't have significant trouble with most diseases or cancer anymore.

To make the results of such a process that would re-engineer someone's DNA appear instantly would be heavily dependent on the process, would it not?
After all you can't just alter the DNA of every cell already in place all at once. Such a process would be akin to magic.

To conclude:

We do not even know how to change an organisms DNA to achieve specific new traits. So answer to how we make the results appear instantly is that we know even less about that.
You assumed too much already known for your question to be answered scientifically.


Let's assume that you know exactly which parts of the DNA to change, thereby bypassing the objections in artificialsouls' answer.

Your issues still are:

  1. Getting that DNA to change in all relevant parts of the body on short notice.

So if you want to change something in the liver, you would need (at least) to affect all liver cells. What comes to mind is e.g. using a virus that targets the liver cells and updates their DNA with Crispr-like techniques.
I assume this would take several days.

  1. The expression of the DNA, i.e. the change in genotype resulting in the desired change in phenotype is not instantaneous either.

In your finger example, theoreticaly you would have to cut off the hand and allow it to regrow. But that will not happen in ordinary humans. For a smaller change, say changing the skin pigmentation, removing part of the skin and letting it regrow would be possible. But you would still be limited to the time it takes the body to repair the wound, i.e. several days up to a week.

  • $\begingroup$ I agree, genetic modification through a virus is possible, to my knowledge - i just don't know to which extend. You can do it with bacteria and such, but i don't know if an organism with an immune system would just accept such a thing without attacking it's own modified cells since you would need a lot of modification for the effect OP asks for. $\endgroup$ Commented Jun 21, 2018 at 12:14

There are existing technologies like Crispr-Cas9 that allow making changes in genes. See Wired article for popular science take on the topic. The technology to change the DNA of cells exists and will continue to develop. So it is not a question if we can do it, the real challenge is figuring out what kind of changes can be done.

Once the changes are made to the DNA, their effect will not be instantaneous and may well result in catastrophic failure of the cell. Splicing in parts of spider DNA will not make you shoot out the web, it will most likely make your nose fall off before you die painfully.

More plausible way to make radical alterations in DNA might involve growing new body and then transferring the conciousness over (hand-waving...).


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