Spread of a De Novo RNA Sequence

Figure WN18.3. The rate of spread of replicating RNA molecules along a capillary tube. Each RNA sequence establishes a pair of wave fronts that propagate at varying speeds. To the right (yellow), one variant was established early on and rose to high concentration. As it spread, a slightly fitter variant was established, causing an increase in wave speed (upper right arrow). When this sequence met other variants, it replaced them and slowed slightly (lower left arrow). The increasing concentration of RNA is shown by the color change from black to yellow. The figure shows superimposed images of the changing concentrations over time. Time is shown running downward, and the distance that RNA molecules have spread along the capillary tubes is shown along the horizontal axis. (From McCaskill and Bauer 1993, Fig. 3i.)