Fig. 5

Deletion maps support a strand displacement mode of mtDNA replication. Deletion patterns were compared to four replication modes. a–d Heavy and light strands are shown in red and blue, with template strands darker. Arrows indicate 5′-to-3′ synthesis directions. Continuously and discontinuously replicated strands are shown as solid and dashed, respectively. Potential heavy and light strand replication origins (labeled oH and oL) are indicated by triangles (gray when unused). See the “Results” section for detailed descriptions of the a strand displacement mode, b the rolling circle mode proposed for Caenorhabditis elegans mtDNA, c a unidirectional, strand-synchronous mode as proposed for Drosophila mtDNA and older RITOLS and Bootlace modes, and d strand-coupled DNA replication. e Deletion arcs, scaled by individual deletion frequency and colored by terminus frequency in 100 bp bins, cluster near oriL and the 3′-terminus of 7S-DNA. See Supplemental Arc Plots for all Gvar samples. f–h Heavy- and light-strand-5′-terminus frequencies (lighter blue and red; 250 bp bins; excluding deletions with TMH ≥ 10 bp) reveal double-bowtie patterns in Gvar and aged Gwt samples (see 1st PCA component in Fig. 4b). Except in Gwt samples under 65 years of age, these patterns fit replication/deletion Monte Carlo models (darker curves; simulation 6 in Additional file 1: Fig. S6a). f Gvar example M38. g Younger Gwt example M03. h Older Gwt example M17. i Mean deletion lengths, from Monte Carlo regression, increased with age in Gwt (triangles) and Gvar (circles) samples