Actually, no. Our DNA does not contain a code "grew a tail", it has "if the cell recieves signal B43221, it has to split 4 times in direction signal comes, then send signal B49112 around..."

For example, humans lack one because two of signals in sequence are broken.

So, to make human grew tail/fur, you have to crack code, and write anew your own. "I lost my tail, have to grew new one". It's complicated because mammals have weak regeneration abilities.

Or, you can "fox" (sorry, "fix") those broken code by CISRP, nothing visible for humans, but next generation will be born with tail, fur, pointed ears and claws. See "Sweet Tooth" for sample.

Ok. Could we use something similar to nano bots, where a bacteria is programmed to search for specific types of cells, but it would be more like a controlled pathogen? Could it try to locate and go to where the stem cells are produced, and, similar to viruses that already exist, reprogram them? But instead of making them replicate itself, it would code them to begin growing bone and extra tissue that would, over a few generations, become a tail. It could also have similar variants that would grow fur, pointed ears, and elongate the jaw into a snout. Then, it would notify the immune system that it was a virus without putting up a fight, to prevent any other complications, such as decreasing the amount of naturally occurring “human cells”. Would that work?

There are no "human cells", just cells which execute some program. Generally, humans are just blad apes with big brains, nothing /specific/. And our big brains are juct change in a neuron development code from "split 5 times then become a neuron" to "split 8 times". So, by fixing some soft inside they remain same human cells.

The virus you speak about was already made, it called Zolengma, cures some genetic disorders and costs 1m$ per dose. If lack of tail/fur/snout (which our ancestors had!) count as a genetic disorder, there could be made furry version of it. To make next generation furries. They will be humans for all other genetic tests.

But - the problem for already born is regeneration. We (almost) lack this ability, it has to be written from scratch. And this is hard, because any error should result cancer instead of crowing new limb. Ad I know, there are researches in dentists area, still no good results.

Thank you for the in-depth explanation. I didn’t mean human cells, but I meant the normal cells that were already there. But I should have said that. Sorry, and thank you.