The uniqueness of the imprinting mechanism.

An epigenetic imprinting mechanism that is based on a gamete-specific methylation imprint restricts expression of a subset of mammalian genes to one parental chromosome. Recent results suggest that imprints may act only indirectly to induce monoallelic expression of coding genes. Instead, atypical non-coding RNAs appear to be a primary target of the imprints, and their parental-specific repression correlates with parental-specific expression of linked coding genes.