The Relevance of Noncoding DNA Regions:

[M]ost of the genome that does something significant and can thus mutate in ways that cause harm is noncoding. We don’t understand that component as well. Certainly I don’t. A rough estimate would be that 1.5% of the genome makes proteins while another 3.5% does something else functional - regulation of protein expression, regulation of other regulators, etc.

Gregory Cochran

http://westhunt.wordpress.com/2012/10/17/more-to-go-wrong/