Sample correlation matrix and hierarchical cluster analysis of gene expression profiles after electroporation. A sample correlation matrix (upper panel) between groups, which had been electroporated or not, was built on the basis of the original two-way hierarchical unsupervised clustering. Red indicates high correlation and blue represents less correlation. The original hierarchical unsupervised clustering (lower panel) was performed with a distance measure of 1 – Pearson correlation coefficient and centroid linkage with a P-value threshold of 0.05 for significant sample clusters and significant gene clusters. The columns indicate the treatment condition and the rows indicate the individual genes, listed with their Genbank number. Increases and decreases in mRNA expression levels are represented by shades of red and blue.