the expression of a set of genes under various conditions, with the purpose of, for example, distinguishing different type of cells or investigating cell/tissue response to treatment. Whole transcriptome profiling has particular value in studies of the genome functioning in different conditions (developmental, environmental, health), especially when large-scale gene expression changes in many genes are expected a priori. Correspondingly, when different conditions are compared to each other (e.g., health vs. disease or young vs. old), genome/gene expression profiling enables researchers to formulate hypotheses regarding the involvement of particular genes whose expression is different in different groups, such as candidate genes for processes that differentiate the groups (e.g., getting ill vs. being healthy or getting old vs. staying young).
