Fig. 3. COBRA of imprinted genes. PCR products of each DMR region were digested with restriction enzymes with a recognition sequence containing CpG in the original unconverted DNA. Where the enzyme sites are methylated, PCR products are fragmented; where PCR products are not fragmented, the enzyme sites are unmethylated. White arrowheads indicate the sizes of the unmethylated DNA fragments. Black arrowheads indicate the sizes of the methylated DNA fragments. The enzymes used to cleave each locus are indicated in parenthesis. BsiEI was used to analyze the Rasgrf1 DMRs in the DNA from mouse pups and from mGS cells. Levels of percentage methylation, estimated by the intensity of each band, are indicated below the gels. U, uncleaved; C, cleaved.