Consider an experiment in which nuclei were isolated from brain, liver, and muscle tissues. the nuclei were incubated with α - [ 32 p ] utp under conditions that allow rna synthesis, except that an inhibitor of rna initiation was present. the radioactive rna was isolated and annealed to various dna sequences that had been attached to a gene chip. in the diagrams of the gene chips, the shading intensity represents the amount of mrna attached, or hybridized, to each dna sequence.