What is the definition of a mutation?
There are two alleles that determine the sensitivity of a person to Coumadin (a medicine for blood thinners used to treat a stroke etc). Sometimes you encounter the terminology that one has a *mutation* on both alleles (father's and mother's side). But why is that called a mutation and not just a *variation*? Does a mutation mean that it *changed during lifetime*, or is the difference between mutation and variation arbitrarily defined? Or is there really a kind of standard taken where deviations are considered to be mutations?