Hierarchical Clustering: Step 2

Next, we average the log-transformed expression levels for the clustered genes (in this case, B and D) and recalculate the similarity scores:

The similarity scores for genes A, C, and [BD]
	Gene A	Gene C	Gene [BD]
Gene A	1	−0.633	0.564
Gene C	−0.633	1	−0.305
Gene [BD]	0.564	−0.305	1

We pick the next highest score, A and [BD], to form the cluster [ABD]. Since we have only four genes, we are done, but this is an iterative process until we are left with a single pair. The end product is a dendrogram, a graphic representation of clusters:

A dendrogram showing that Gene B and Gene D are the most closely related, followed by Gene A and Gene C.