Prevalence of control region heteroplasmy in mtDNA for buccal swab and blood tissue samples taken from the same individuals.

All variants are base substitutions (at a single point or within a specified sequence range), except VRII 523 to 524, which is an insertion-deletion. p-values are reported for a 1df robust logistic regression (standard error of the beta coefficient calculated clustered by twin pair) contrasting prevalence of heteroplasmy between buccal and blood samples. HVI = hyper-variable region I; HVII = hyper-variable region II; VRI = variable region I; VRII = variable region II.