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RNA-only genes: Are lincRNAs the links in the chain?

From the Economist:

Once, and not so long ago, received wisdom was that most of the human genome—perhaps as much as 99% of it—was “junk”. If this junk had a role, it was just to space out the remaining 1%, the genes in which instructions about how to make proteins are encoded, in a useful way in the cell nucleus.

That, it now seems, was about as far from the truth as it is possible to be. The decade since the completion of the Human Genome Project has shown that lots of the junk must indeed have a function. Almost two-thirds of human DNA, rather than just 1% of it, is being copied into molecules of RNA. As a consequence, rather than there being just 23,000 genes (namely, the bits of DNA that encode proteins), there may be millions of them.

One new genetic class is known as lincRNAs. Molecules of lincRNA are similar to the messenger-RNA molecules which carry protein blueprints. They do not, however, encode proteins. More than 9,000 sorts are known, and most of those whose job has been tracked down are involved in the regulation of other genes, for example by attaching themselves to the DNA switches that control those genes.

LincRNA is rather odd, though. It often contains members of a second class of weird genetic object. These are called transposable elements (or, colloquially, “jumping genes”, because their DNA can hop from one place to another within the genome). Transposable elements come in several varieties, but one group of particular interest are known as endogenous retroviruses. These are the descendants of ancient infections that have managed to hide away in the genome and get themselves passed from generation to generation along with the rest of the genes.
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