An expressed-sequence tag (EST) is a stretch of DNA sequence made by copying a portion of an mRNA molecule. As such, all ESTs replicate sequences from genes. They were first proposed as a useful way to find genes in the genome in 1991. A relatively small portion (approximately one-tenth) of the human genome is thought to be transcribed, or "expressed", and looking at ESTs is a way to home in on the expressed, clearly functional sequences in the genome that the nucleus sends out to the rest of the cell.
Adams, M.D., Kelley, J.M., Gocayne, J.D., Dubnick, M., Polymeropoulos, M.H., Xiao, H., Merril, C.R., et al. Complementary DNA sequencing: expressed sequence tags and human genome project. Science, 252:1651-6. 1991. [PubMed]
Last Reviewed: May 6, 2013