GENOMIC IMPRINTING AND MAMMALIAN DEVELOPMENT

Genomic imprinting, which results in the mono-allelic expression of ce rtain genes in a parent of origin-dependent manner, represents a speci alized form of gene regulation which may be vitally important for mamm alian development. The mechanisms which underlie imprinting and the mo lecular nature of the imprint itself remain elusive but most likely in clude epigenetic modifications of DNA, such as methylation and chromat in structure changes. It is clear, however, that many of the known imp rinted genes play important developmental roles and that changes in th e functional imprinting of some of these genes may have important path ological consequences, including placental abnormalities. (C) 1996 W. B. Saunders Company Ltd