An Augustinian monk named Gregor Mendel was the first person to make precise observatıons about the biological mechanism of inheritance.This happened a little over a hundred and thirty years ago in an Austrian monastery, where Mendel spent his leisure hours performing experiments with pea plants of different types.He crossed them carefully and took notes about the appearance of various traits, or characteristics, in succeding generations.From his observation,Mendel formed a set of rules, now known as the ‘ Mendelian Laws of İnheritance,’which were found to apply not only to plants but to animals and human being as well. This was the begınnıg of the modern science of genetics.