Test for hexamers over-represented in a position-independent manner. (A) Over-represented in late G1: ACGCGT. The height of the white bar represents the number of genes in each of the five cell cycle-regulated data sets. The purple shading indicates the number of upstream regions in that data set that contain one or more copy of the oligomer. The number of upstream regions expected to contain that sequence element, if the element were evenly distributed among all five data sets, is marked with the pink box. The blue line indicates the contribution that each data set makes to the χ2 score. (B) Not over-represented in any phase: GATGTA. Ninety-four cell cycle yeast upstream regions contain one or more copy of the sequence ACGCGT, and a different set of 94 contain one or more copy of the element GATGTA. However, these elements are distributed differently among the five data sets. The element ACGCGT, which has a χ2 score of 60.4, is over-represented in late G1—the observed number of elements (purple) is greater than the expected number (pink). It is also under-represented in G2 and M, as the observed number is less than the expected number. The score in those three phases (blue) is thus higher than it is in early G1 and S. The element GATGTA, which has a χ2 score of 4.9, is not significantly over- or under-represented in any data set.
