Simulation including a positively selected locus.

<p>Panels A-D represent the results of four independent simulations with selection. Black regions represent not-yet-colonized areas of the esophagus, and small black dots represent crypts which have died and not yet been replaced. Colors indicate the first three principal components of a PCA analysis of crypt genotypes at 100 neutral loci, essentially labeling distinct clones or cell lineages. Initial seeding of the esophagus was in the bottom-center of the figure. The left and right sides of the image wrap around. Arrows indicate clones carrying a selectively advantageous mutation. These images were chosen from a larger collection to illustrate typical selection signatures and do not represent a random sample. Selected clones appear more homogeneous and are round in shape whereas clones which expanded neutrally are wedge-shaped.