Comparison of the distribution of fluorescence in microarrays with homologous (C, chicken) or heterologous (NI1 to NI4, never-immersed penguins and SA1 to SA3, sea-acclimatized penguins) hybridizations. All samples were hybridized on Affymetrix GeneChip® Chicken Genome Arrays. Data for the homologous hybridization (C) were downloaded from the Gene Expression Omnibus (GSM157808). A: Fluorescence intensity boxplot. B: Fluorescence intensity density plot.