Comparison of gene expression noise and DNA methylation between studied tissues (A) Comparison of mean transcriptional noise between the two tissues. The brain exhibits significantly lower transcriptional noise compared to blood (paired t test, P <0.001). (B) Methylation levels, however, are significantly higher in the brain compared to blood (paired t test, P <0.001). We only used genes for which methylation and transcriptional noise data exist in both tissues (total no. of genes = 3,644).