I suspect it's not widely known that (or how much) genetic variation that would otherwise be deleterious is "hidden" by buffering. Much of that is accomplished by a protein called Hsp90. I've written a feature for Nature about it.
www.nature.com/articles/d41...
Biology has clever ways to mask the effects of potentially harmful gene mutations. Scientists are investigating how this ‘buffering’ works — and how to exploit it.
