Toxoplasma mRNA pools have a distinctive composition. [A] The mRNA abundance classes in Toxoplasma were characterized in comparison to SAGE datasets obtained from yeast, and from human libraries constructed from heart, lung, liver, muscle and cerebellum. For each comparison, unique SAGE tags are plotted in reverse order as a fraction of total unique tags in the library beginning with the highest frequency tags (X-axis). These results were plotted against the concentration for each unique tag, defined as the fraction of the total SAGE tag concentration for that library (Y-axis). [B] Abundant SAGE tags corresponding to highly expressed mRNAs fall into a number of functional classes  with unknown genes (not displayed here) and apicomplexa-specific genes involved in parasite invasion the dominant categories for Toxoplasma. [C] Venn diagram displaying SAGE tags belonging to three distinct classes; high abundant tags in the 2 × 2 dataset (red), tags uniquely up- or down-regulated in one of the six developmental libraries (green), and Apicomplexa-specific SAGE tags encoding proteins found in dense granules, rhoptries, micronemes and on the parasite surface (blue). [D] Anti-sense transcription in relation to SAGE tag abundance. The ratio of antisense versus sense was determined at each genomic locus using GeneFinder gene prediction dataset derived from Me49B7 genome sequence. Levels of 'antisense' as fractions of the 'sense' transcription were quantified for each gene prediction dataset and plotted against the frequency of the sense tag. Similar plots were obtained using three other gene predictions from TwinScan, TigrScan and Glimmer (not shown).