Figure 1. Hierarchical clustering diagram. The study aims to identify the genes expressed differently in normoxic (control) and hyperoxic conditions in the superior and inferior halves of the retina because regional sensitivity to hyperoxia of the inferior was expected. Clustering analysis demonstrated similarity and correlation between replicates within an experimental group and between different groups. Each column comprises a set of horizontal lines with each line representing a single gene or noncoding RNA (ncRNA). The color given to the line depends on the level of expression of the gene, from blue (low expression) to red (high expression); the range of colors available is shown at left. In each column, the genes are arranged in low-to-high expression, going down the column. The program then compares the order of genes in the column and indicates, by the brackets at top, the similarities and differences between the four samples. The replicates of each sample clustered closely to each other (not shown) and were averaged to constitute the four samples shown. The samples from the superior retina before and after hyperoxia were most similar. The sample from the inferior retina after hyperoxia, in which photoreceptor degeneration was greatest, is most dissimilar from the other samples.