How does whole genome bisulfite sequencing (WGBS) work?

Genomic DNA is treated with sodium bisulfite selectively, which alters unmethylated cytosines, converting them into uracil. Methylated cytosines remain unaffected. Following PCR amplification, uracils are converted into thymines, leaving methylated cytosines intact. Methylcytosines are cytosine bases with methyl groups added to their C5 position. This chemical alteration allows researchers to distinguish between methylated and unmethylated cytosines, aiding in the analysis of DNA methylation patterns across the entire genome.