Two PCRs are then carried out on the modified DNA , using primer sets identical except at any CpG islands within the primer sequences .
DNA is first treated with sodium bisulfite , which converts unmethylated cytosine bases to uracil , which is recognized by PCR primers as thymine .
Two PCR are then carried out on the modified DNA , using primer sets identical except at any CpG islands within the primer sequences .
DNA is first treated with sodium bisulfite , which converts unmethylated cytosine bases to uracil , which is recognized by PCR primers as thymine .