Methylation and genetics. One of the most common and most important genetic mutations/polymorphisms in the Australian population affects several enzymes crucial to methylation. The most commonly affected enzyme is called MTHFR*1. Less commonly the MTR*2 and MTRR*3 enzymes are affected (and there are more). If we are unlucky enough to inherit the damaged MTHFR gene from both our parents, we reduce our ability to methylate by 70%! If we inherit only one defective gene we have a 30% reduction in our ability to methylate. Ask Dr Alice if you would like to find out if you have a genetic methylation problem.