Investigators are studying gene X, whose expression is controlled by a set of three regulatory DNA sequences that lie upstream of the gene's coding sequences. In an intact organism, gene X is expressed in cell types B, E, and F.
To begin to dissect how these regulatory sequences influence the gene's expression in different cell types, the investigators construct a series of recombinant DNA molecules in which different combinations of these regulatory elements control the expression of a reporter gene, Y. These recombinant molecules are then tested for expression in cells. The effects they have on the expression of the reporter gene Y are shown in the diagram.
Based on these data, what can be concluded about these regulatory DNA sequences?