Plasmodium yoelii 17X blood-stage parasites express a large number of yir and pyst-a during infection. Animals were infected with P. yoelii 17X iRBCs and parasite RNA was collected under various experimental conditions (see Methods). P. yoelii DNA microarrays were completed and a normalized mean fluorescence intensity for all genes spotted on the P. yoelii array was calculated and percentiled (A). Number of yir (B) and pyst-a (C) genes in the listed percentile ranges were calculated considering a set of 464 yir gene oligos and 74 pyst-a oligos that could detect unique transcripts. The number of yir or pyst-a genes expressed (i.e., those with a mean fluorescence intensity above the 50th percentile) is listed at the top of the Figure above each experimental condition.