A review with 4 refs. The authors discuss a few examples that illustrate the drastic effects that genome imprinting can have on the phenotypes of progeny. There are at least a few genes whose phenotypic expression depends upon the parent from which they have been inherited. Thus, the differential manifestation of a few of the paternal or maternal genes/chromosomes in the progeny has shown yet another dimension to our understanding of the mechanisms of inheritance by annulling the principle of equivalence of reciprocal hybrids. In short, sometimes it does matter from which parent a gene is inherited. Imprinting is not a permanent change or a mutation in the DNA, but rather a temporary alteration in the functional status of the DNA. Imprinting is defined as an epigenetic, gamete-of-origin dependent modification of the genome. This is also referred to as reversible silencing of genes. Since genome imprinting is implicated in the inheritance of several complex human disorders, it has become important in the area of clin. genetics. [on SciFinder(R)]