Serial analysis of gene expression: ESTs get smaller.

Measuring gene expression on a global scale has been one of the vexing problems of cell biology. Velculescu et al.(1) recently proposed a system for identifying gene expression levels based on very short sequence tags-about nine base pairs-located at a specific site within a gene transcript. By coupling the strategy to current automated sequencing machines and the large expressed sequence tag databases, it should be possible to follow changes in gene expression for large numbers of genes economically and accurately.