Graphical representation of experimental design of the microarray experiment. The nodes correspond to RNA from samples with high expected differential gene expression (rat cell lines NRK52E and AR42J) compared to self-self hybridization (rat cell line AR42J). The samples were hybridized to rat 15 k cDNA duplicates under six different blocking conditions including no blocker, 1000 ng poly(dA)40–60, and 25 to 1000 ng LNA dT blocker. Dye-swap and self versus self were performed for all blocking conditions (total of 24 hybridizations). Green-labelled samples are placed at the tail and red labelled samples at the head of the arrows.