As far as I've seen, this expression is almost always used in
relation to gene expression profiling. Unfortunately, I have no
background in this area. Can someone please explain this in
layman terms? Although each cell of your body essentially
contains the same DNA and the same genes, cells in different
tissues express (turn on) different genes under different
conditions. Measuring differential gene expression involves
looking at the amount of expression for a gene (or set of genes)
in two contrasting scenarios. The contrast could be across
different times, different tissues, different conditions,
different related species, etc. When, you say a gene is
"differentially expressed", this is very context-specific. The
phrase means nothing by itself, and it is only useful in terms
of the applicable contrast. For example, the statement "gene A
is differentially expressed" is uninformative, while the
statement "gene A is differentially expressed in liver and
muscle tissue" is descriptive--it tells you that liver tis