Figure 1: During mammalian gametogenesis, the diploid primordial germ cell undergoes meiosis to produce haploid male and female gametes. As meiosis progresses, specific DNA sequences acquire a DNA methylation imprint (black lollypops) in one parental germline but not the other. After fertilization, this imprint is recognized within the somatic cells establishing an imprinted domain. Maternal inheritance is indicated in red and paternal inheritance is indicated in blue.