So-called junk DNA might regulate the activity of the genes they surround

Anjana Ahuja:

Itstrickytounderstandthissentenceisntit? If you pluck the punctuation out of a sentence, it becomes much harder to read. Biologists now suspect that some stretches of DNA in the human genome that were previously thought to be useless might serve as punctuation between genes.

Your genome – the genetic material that makes you, you – is made up of genes and so-called junk DNA. Genes are the instruction manuals that your body uses to make proteins. But genes constitute only 4 per cent of the genome. The rest – the junk DNA – appears to serve no useful purpose. In the jargon, it doesn’t code for anything. This is puzzling, because scientists thought that evolution would fine-tune the human genome to preserve the essential bits and discard the rest.

Now an international team of scientists has discovered that junk DNA might regulate the activity of the genes they surround. While genes do the hard work of making proteins, the junk DNA could be responsible for starting and stopping protein production. “Some of the junk DNA might be considered punctuation marks – commas and full stops that help make sense of the coding portion of the genome,” says Dr Victoria Lunyak, of the University of California, San Diego, School of Medicine, one of the authors of a paper published in Science. Another analogy is to think of genes as building labourers, and the surrounding pieces of junk DNA as foremen.

This could explain why gene therapy has had limited success: scientists have tended to transfer genes without the junk DNA. And we know what happens when a foreman doesn’t turn up on a building site: you get the tea-drinking and wolf-whistling, but not much building.

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