Fig. 9.

Parental imprints are established during oogenesis or spermatogenesis at sequence elements that control the imprinted expression (the ICRs). After fertilization of the egg by the sperm, these imprints are maintained throughout development. DNA methylation (lollipops) is the most consistent hallmark of imprints. Two examples of ICRs are depicted: one with paternally derived (ICR1) and one with maternally derived (ICR2) DNA methylation. [Reprinted from K. Delaval and R. Feil: Curr Opin Genet Dev 14:188–195, 2004 (52), with permission from Elsevier.]