Approximate percentage of FMDV genomes carrying a specific residue at a defined position during serial passages in competition experiments. The global sequence of the viral populations obtained after each passage was determined by automated sequencing, and the relative abundance of each residue type at the positions of interest was estimated from the ratio between the integrated areas of the corresponding bands in the chromatograms, as described in Materials and Methods. (A) Competition between the M3014L mutant and the parental virus. Circles, Met; squares, Leu at position 3014. (B) Competition between the D3009A/M3014L mutant and the parental virus. (B.1) Circles, Ala; squares, Asp at position 3009; black inverted triangles, Leu; black triangles, Met at position 3014. (B.2) Squares, Thr; circles, Pro at position 1104. (C) competition between the C3007V mutant and the parental virus. (C.1) Squares, Val; circles, Cys at position 3007. (C.2) Squares, Ala; circles, Asp at position 3009. All three competition assays were carried out in duplicate or triplicate with very similar results.