" Mice were often the first test subjects for these techniques, and scientists were amazed at how effective the new methods were in the tiny creatures. By injecting new DNA into fertilized mouse eggs and then implanting those eggs into female mice, researchers found they could permanently splice the foreign DNA into the next generation and cause observable changes in the developing animals. These advances meant that any gene that scientists could isolate and clone in the lab could be tested and investigated; by adding the gene to cells, scientists could observe its effects and better understand the gene’s function "

― Jennifer A. Doudna , A Crack in Creation: Gene Editing and the Unthinkable Power to Control Evolution