Measuring Expression Profiles: Step 1. Isolating the mRNA
There are two different ways to capture expression profiles, by measuring either the mRNA or the protein molecules. CGAP measures the mRNA molecules.
First, the mRNA molecules must be separated from all the other cellular molecules. Each mRNA has a unique label attached at one end, a short length of A bases (polyA) strung one after the other. Scientists take clever advantage of this feature. They create a stationary support holding short chains of polyT bases. As the cell's content passes over the support, the polyA ends of the mRNAs base pair with the chains of polyT. This isolates the mRNAs.
Unfortunately, the mRNA molecules are not very stable and may be present in very small amounts. So, having captured the mRNAs, scientists quickly convert them into something more stable and easily measured.