Relationship between the DNA methylation state of CpG islands (CGIs) and their location relative to transcripts in the oocyte. Almost all CGIs that are unambiguously associated with the promoter of an oocyte transcript are unmethylated. In contrast, a large majority of the CGIs that are unambiguously (distal) intragenic become methylated in the oocyte. CGIs that do not overlap oocyte transcripts were similarly classified according to their location relative to annotated genes (UCSC Known Genes). They illustrate that in the absence of actual transcription, there is no close relationship between CGI gene-relative position and oocyte methylation. The numbers underneath each category are the total number of CGIs in the respective class.