ABSTRACT
In the pre-Mendelian era, inheritance was believed to be a merging of characteristics of both parents. Mendel’s experiments indicated that the reciprocal crosses between parents with contrasting characters produced the same results. But there was existing evidence showing that reciprocal crosses may not always be alike. A classic example is a cross between a female horse and a male donkey, which produces a mule, whereas the reciprocal cross produces a hinny. No suitable explanation was available until lately when the signicance of epigenetics started to be realized. In the Greek language, the prex “epi” means features that are “above” or in addition to something. Therefore, epigenetic traits exist in addition to the traditional molecular basis for inheritance.
