Qualitative analysis of gene expression. The bar chart depicts over-represented GO terms obtained from the list of differentially-expressed genes obtained in single chemical and mixture exposed samples. Enriched terms were selected through hypergeometric statistics comparing the GO term distribution in each gene list and the whole set of mussel sequences printed onto the array (Fisher exact test, p < 0.05) . Bar length represents the relative frequency (%) of a GO term in each analyzed condition. Shown is also the number of genes associated with each GO term.