Differential gene expression between red and white porcine muscles. A. An illustration of a two-colour hybridisation. There were 48 such grids on each microarray slide. Each clone was printed twice. Clones on the top half were duplicated in the lower half of each grid. With some spots, the surrounding background was higher than the signal of the corresponding spots. B. Scatter plot displaying the median expression profile of all genes represented on the microarray, based on seven replicate slides. Genes equally expressed in red and whites would be positioned along the middle line (1). Points above the +2 or below -2 represent genes that were at least 2-fold more or less highly expressed in the psoas than the LD.