(A) Quantitative PCR shows the DNase I treatment we used was stringent enough to eliminate both mtDNA and nuclear DNA from SH-SY5Y cell-generated genomic DNA samples. (B) Quantitative PCR shows DNase I treatment of the plasma exosome fraction does not fully eliminate mtDNA or nuclear DNA from the fraction. (C) DNase I treatment consistently increases the plasma exosome fraction mtDNA:nuclear DNA copy number ratio. For the control region amplification, the ratio derives from absolute copy numbers. For the mt-tRNALeu and ND1 amplifications, the ratios derive from relative copy numbers. (D) In an NT2 cell-derived exosome fraction, DNase I treatment does not eliminate all mtDNA amplification, eliminates most nuclear DNA amplification, and increases the mtDNA:nuclear DNA ratio. Ctrl=control.