The Hardy-Weinberg principle is not generally found in nature because it requires certain conditions in an environment. These conditions are the absence of the things that can cause evolution. In other words, if no mechanisms of evolution are acting on a population, evolution will not occur--the gene pool frequencies will remain unchanged.
Some pregnant women experience a metallic taste in their mouth during the early stages of pregnancy, because of the hormone changes. It's also fairly common to crave certain foods, or go off certain foods, and have a heightened sense of smell.
A metallic taste in the mouth is a common complaint and can be due to a variety of causes-from medication you may be taking to dental problems. In the absence of other symptoms, it is unlikely that a metallic taste in your mouth indicates serious disease.