The S and M clusters. The transcription profiles are displayed as described in the legend to Figure Figure1.1. (A) Histone cluster. The eight genes encoding histones and the yeast histone H1 homologue cluster very tightly and are expressed during S phase of the yeast cell cycle. (B) MET cluster. The expression of many of the members of the methionine pathway peaks just after the histones. (C) CLB2 cluster. A subcluster of genes that are expressed similarly to CLB2 highlights genes that peak during M phase.