The final step in the process of capturing an expression profile is to identify the cDNA molecule in each clone. This is done by determining the order of, or sequencing, the bases in the cDNA. Fortunately, rather than sequence every base, scientists need only sequence about 400 bases at the polyA end to uniquely identify the entire cDNA. This short sequence is called an "expressed sequence tag" or EST, and its sequence information is stored in a public database for everyone to use.

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