Genomes are typically littered with "junk": stretches of DNA with no obvious function that are scattered among genes. But scientists are now finding that some of this junk, at least that from lower organisms, can be astoundingly useful to people, if apparently not to the organisms that carry it. This surprisingly handy DNA is located within genes and not in the no man's land between one gene and the next. It comes in two types. So-called introns are clipped out of a gene's RNA before a protein is made. By contrast, the less well known inteins are translated into protein but then immediately removed.
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