The differences in gene expression profiles as measured by Pearson correlation and the fast Fourier transform (FFT) phase are low between all strains measured here. (A) Depicts the distribution of the Pearson correlation between gene expression profiles from the 3D7 and HB3 datasets. 70% of the correlations are greater than 0.7. The inset plots the nearly linear relationship for most of the FFT phases for these two strains. The largest differences in phase are within the red circles. The arrows point to a gene with a significant change in phase between 3D7 and HB3 (MAL13P1.344) and another gene with virtually no difference (PFI1740c). The Pearson correlation and phase change between 3D7 and HB3 for these two genes are shown with the expression profiles from all three strains (B). Northern blot of MAL13P1.344 (C) shows mRNA transcript levels at the ring (R) and schizont (S) stages of development for the 3D7, Dd2 and HB3 strains of P. falciparum. Transcription of this gene in HB3 is out of phase with that measured in 3D7 and Dd2.