A genome is not a blueprint for building a human being, so is there any way to judge whether DNA is junk or not?

Itai Yanai and Martin Lercher in Aeon:

ScreenHunter_775 Aug. 27 17.53Humans are astounding creatures, our unique and highly complex traits encoded by our genome – a vast sequence of DNA ‘letters’ (called nucleotides) directing the building and maintenance of the body and brain. Yet science has served up the confounding paradox that the bulk of our genome appears to be dead wood, biologically inert junk.

Could all this mysterious ‘dark matter’ in our genome really be non-functional?

Our genome has more than 20,000 genes, relatively stable stretches of DNA transmitted largely unchanged between generations. These genes contain recipes for molecules, especially proteins, that are the main building blocks and molecular machines of our bodies. Yet DNA that codes for such known structures accounts for just over 3 per cent of our genome. What about the other 97 per cent? With the publication of the first draft of the human genome in 2001, that shadow world came into focus. It emerged that roughly half our DNA consisted of ‘repeats’, long stretches of letters sometimes found in millions of copies at seemingly random places throughout the genome. Were all these repeats just junk?

More here.