Knockout rat

So imagine you have a rat, and this rat has a special gene inside of it that scientists want to study. But it's really hard to study the gene when it's inside the rat's body, because one gene is connected to a whole bunch of other things in the rat. So, the scientists come up with an idea: what if they could take out that special gene and see what happens?

That's where the knockout rat comes in. Scientists use special techniques to remove or "knock out" that special gene from the rat's DNA, so that it's not in there anymore. Then they can study the rat without that gene, and see what differences there are. Maybe they notice the rat has different behaviors or looks different or gets sick more often. Whatever it is, they can see how that special gene was affecting the rat before.

So, a knockout rat is just like a regular rat, but with a specific gene intentionally taken out so that scientists can study its effects.