>>scientific parlance, linkage disequilibrium

For anyone feeling challenged by that term, it just means that if one of the alleles is present, the distribution of the presence (or absence) of a second one is not random.

>>warfarin... Bloody Neanderthals

I see what you did there :) For anyone else, warfarin is a clot-suppressing drug, an overdose might, at a minimum put the patient in the same position as a hemophiliac (like some of the very-inbred royal European houses, leading to the English epithet "Bloody... [insert term here; it's usually 'hell', but the English can be quite creative].

Also, anything that affects cytochrome P450’s ability to break down substances is going to change dwell time of a lot of drugs. Good explanation here.