Binding site frequencies. The distribution of various promoter elements in the upstream regions of each the five cell cycle–regulated groups and a control group of 279 non-cell cycle–regulated genes that do not respond to either Cln3p or Clb2p induction are graphically displayed. In each case the numbers on the x axes represent distance from the start codon, and the bars represent the frequency of a particular site per residue per gene at that position in the upstream promoter regions. N is any base; Y is C or T; W is A or T; R is A or G; and M is A or C. (A) SCB. (B) A variant on the SCB, which is also similar to an MCB. (C) MCB. (D) MCB_d, a degenerate MCB sequence. (E) MCM1/SFF site. (F) Swi5e, an extended Swi5 site.