Next, we compared, among the ethnicities, the degree of methylation at each of the CpG sites. We found significant experiment-wise differences in the degree of methylation for the −25 and the +12 CpG sites in the controls among the three ethnicities (Table 3). For the −25 CpG site, the percent methylation was similar in African-American and the previously reported Caucasian controls (33.9, 32.7%, respectively), and was higher than that found in Hispanic controls (23.4%) (experiment-wise P = 0.0249). The highest level of methylation at the +12 CpG site in the controls was in the African-Americans (12.2%) and was found to be lowest in the Hispanics (4.7%) (experiment-wise P = 0.0080); it was intermediate in the Caucasians (6.6%).
