One classic way to understand the importance of a particular component of a system is to take that component away and see how the system works?
A. Yes. As a matter of fact, it’s a very useful technique. So if one has a gene and wants to know how important it is to function, what one can do is to engineer a targeted gene replacement, a knock-out, and then generate embryonic stem cells — this is often done in mice — and those embryonic stem cells are then fused into an existing embryo. You then, hopefully, grow up a mouse in which there’s a patch of cells that has the targeted replacement. You find a mouse — sometimes it takes a while — in which these targeted replacement cells are in the gonads, in the reproductive organs. So hopefully, you’ve generated a male mouse in which you have the targeted replacement in the testes, a female mouse in which you have a targeted replacement in the ovaries. You cross them. Then you get an offspring in which both genes have been knocked out. And then you can study the effect of losing that gene.
