DNA methylation pattern of L1Md_Tf (L1), major satellites (mSat), and IAPLTR1 (IAP) in cleavage stage mouse embryos. (A) DNA methylation patterns (for explanation see Figure
1) (B) Absolute DNA methylation levels and percentage of hemimethylated CpG dyads in relation to all methylated CpG dyads. Two-cell embryos were analyzed before and after replication, and further-cleavage stage embryos were analyzed at 12-hour intervals to determine methylation changes during replications. DNA methylation pattern remained stable until the morula stage, when a further drop in methylation occurred at L1 and IAP. Interestingly, over the course of the cleavage stages the amount of hemimethylated CpG positions remained equally high.