The G1 clusters. The transcription profiles are displayed as described in the legend to Figure Figure1.1. (A) CLN2 cluster. A fraction of the genes regulated similarly to the G1 cyclin CLN2, which reaches peak expression in the G1 phase of the cell cycle. To view the full cluster of all the cell cycle–regulated genes, visit http://cellcycle-www.stanford.edu. (B) Y′ cluster. Thirty-one genes that are located within the Y′ elements show cell cycle regulation of mRNA levels that peak in G1.