>>13428864there are multiple ways to do this. here's an example
1. start with an integrating virus. these viruses have the ability to stick their DNA into the genome of their victims, convincing their cells to make more virus
2. modify the virus so instead of instructions to make more of itself, it has the instructions to make a glow in the dark protein like GFP
3. let the virus infect your zygote with the gfp gene it's now carrying
4. incubate the zygote, as its cells divide it copies the gfp gene you stuck in it because it doesn't know any better
5. glowing animal!
obviously these steps are pretty complicated and could probably be divided further but that's the basic idea
