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. Author manuscript; available in PMC: 2018 Mar 1.
Published in final edited form as: Reprod Toxicol. 2016 Jul 26;68:72–84. doi: 10.1016/j.reprotox.2016.07.015

Figure 2. The timing of ART procedures coincides with dynamic DNA methylation changes in gametes and embryos.

Figure 2

Controlled ovarian hyperstimulation (COH) allows the maturation of several immature oocytes. DNA methylation is acquired during this period of oocyte maturation. Fertilization and pre-implantation embryo development occur in vitro with commercially available culture media at 37°C and low oxygen conditions. Following fertilization, there is both active and passive demethylation of the paternal and maternal genomes, respectively, in the embryo. Embryo culture and transfer coincide with this demethylation. DNA methylation acquisition occurs promptly in the postimplantation embryo. DNA methylation levels in the extraembryonic tissues are relatively hypomethylated compared to levels in the embryo. IVF=in vitro fertilization; PGD=pre-implantation genetic diagnosis.