is used to obtain high-resolution methylation profiles for a limited number of reference epigenomes, while less thorough analysis is performed on a wider spectrum of samples. This approach is intended to maximize the insight gained from a given amount of resources, as high-resolution genome-wide mapping remains a costly undertaking. Gene-set analysis (for example using tools like DAVID and GoSeq) has been shown to be severely biased when applied to high-throughput methylation data (e.g. genome-wide bisulfite sequencing); it has been suggested that this can be corrected using sample label permutations or using a statistical model to control for differences in the numberes of CpG probes / CpG sites that target each gene. Oxidative bisulfite sequencing 5-Methylcytosine and 5-hydroxymethylcytosine both read as a C in bisulfite sequencing. Oxidative bisulfite sequencing is a method to discriminate between 5-methylcytosine and 5-hydroxymethylcytosine at single base resolution. The method employs a specific (Tet-assisted) chemical oxidation of 5-hydroxymethylcytosine to 5-formylcytosine, which subsequently converts to uracil during bisulfite treatment. The only base that then reads as a C is 5‑methylcytosine, giving a map of the true methylation status in the DNA sample. Levels of 5‑hydroxymethylcytosine can also be quantified by measuring the difference between bisulfite and oxidative bisulfite sequencing. See also Reduced representation bisulfite sequencing References External links Bisulfite conversion protocol Human Epigenome Project (HEP) - Data — by the Sanger Institute The Epigenome Network of Excellence Molecular biology Epigenetics Genomics techniques