A few weeks back I attended a seminar by one of the creators of the World's first “knockout mouse”. Such a creature is exactly like others of its species except that a scientist has removed one or more genes from it, for the usual scientific reason: to see what happens. Back in the 80s, creating such a beastie was a Very Big Deal. Now, if you google for “knockout mouse” you will get a bunch of ads from companies offering to custom breed one for you.
To many people's surprise, one of the weirdest things about knockout mice is that often they aren't weird at all. Some guy in a white coat comes along and chops out a gene that is supposedly “crucial” to, say, the mouse immune system and the resulting mouse grows up to do all the usual mousey things in the usual mousey way, without so much as a bad sneeze.
This week, things got even stranger. Lab mice: they just don't give a toss.