Figure 1From: Gene Expression and Isoform Variation Analysis using Affymetrix Exon ArraysPCA plots at the probe set level show two main sources of variation among the 20 samples. The first principal component explains 65% of the variance and corresponds, as expected, to the biological source of the sample: brain (B) vs. reference (R). The second principal component explains 20% of the variance and corresponds to the "lab effect" between VT (blue), and McGill (red) – that is, it illustrates the technical variability across labs.Back to article page