Differential gene expression is lower than expected in parasites from independent Plasmodium yoelii 17X infections. Groups of animals (n = 5-10) were infected on four separate occasions (I1, I2, I3 and I4) using four separate donor animals. RNA was isolated and transcripts detected using P. yoelii DNA microarrays. The six possible pair-wise comparisons are listed at the top of the Figure and functional categories are listed in the far left column. Up- and down-regulation for each comparison is indicated as described for Figure1.