Serial Analysis of Gene Expression

A technique for gene expression analysis that builds on the random sampling of cDNA libraries.

1. Generate a 'sequence tag' for each mRNA in your collection. This is a characteristic 10-14bp segment that is cut from the mRNA with a type IIs restriction enzyme. Rest assured, there is a favoured type IIs restriction enzyme for this line of work.
2. Join several sequence tags together to form concatemers, which are then cloned and sequenced.
3. Identify the genes responsible for each sequence tag by searching databases (special sequence tag repositories are available eg. from GenBank).

This represents a massive increase in sequence throughput. The sequence tag is long enough to almost always uniquely identify an mRNA (fake proof: 4^14=bignum) if the restriction enzyme we used to select it is known; different restriction enzyme, different sequence tag - which is occasionally useful.