Mouse versus fruitfly
There is some interesting stuff about the comparison between doing this prize with a mouse and doing it with fruitflies (drosophila). A couple of the more interesting points are that in a lab you can cheaply maintain and process larger numbers of fruitflies than mice, and the fruitfly lifespan is much shorter than the mouse lifespan so you get quicker feedback.

But I also understand the publicity argument that people feel more kinship with mice. It's easier as a non-scientist to believe that results in mice are much more relevant to humans. Results in mice will more easily attract funding for subsequent work.

Does it make sense for researchers to work with fruitflies first, and then port their techniques to mice for later 
confirmation and to collect the prize? Hopefully that would take relatively little more time and expense than doing the whole thing with fruitflies. We'd eventually need to port these techniques from mice to humans anyway, so there is a presumption that porting across species is feasible.