Expressed Sequence Tags
What Are They?
Expressed sequence tags, or ESTs, are a type of sequenced site
tag (STS): a segment of DNA around 200 to 500 base pairs long, whose location
on the chromosome and sequence are known. ESTs are created from cDNA,
a single strand of DNA that has been copied from an mRNA template.
In other words, an EST is a strand of DNA consisting only of the exons—the
base pair sequence that is expressed—of a gene.
What Are They Good For?
ESTs can be used by researchers looking for new genes, mapping
genomes, and identifying the coding regions of a gene. In addition,
patents on ESTs will give you rights to the entire gene. Several
companies are stockpiling the ESTs they develop and applying for patents
on them, sometimes thousands at a time, despite usually having no
idea what role the gene plays in the human body. The investment in
finding and sequencing these ESTs is so potentially huge, that these companies
are willing to live with their lack of knowledge about the gene and the
vast number that may eventually prove useless. After all, they can
always follow in Human Genome Science’s footsteps and cash in on the research
of others through royalties and licensing. Wouldn’t you like to be
the company holding the patent or licensing rights to a gene that may lead
to a vaccine against HIV? It could happen; all you need are some
ESTs and a good patent lawyer.
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