Validation and reproducibility. a. Comparison between bisulfite sequencing and pyrosequencing for the first five CSX CpG sites with different hairs. Correlation coefficient is 0.65. b. Comparisons of bisulfite sequencing of eight more bacterial clones from the same PCR (black "X's" and trend line) or from repeat PCR of the same hair (red crosses and trend line). Identical methylation patterns were not obtained with resampling, probably because hair follicles contain complex mixtures of alleles, but correlation coefficients are respectively 0.86 and 0.93.