junk DNA

A region of DNA that apparently contains no genetic information. In recent years the presumed ‘junk’ has increasingly been found to play a role in the regulation of gene activity.

In the human genome, for example, genes only account for 1.1% of approximately 3 billion base pairs, while 24% are introns interrupting these genes; the rest is known as intergenic DNA and is of mostly unknown function.

In 2007, an international research consortium reported results of the pilot phase of the ENCODE project (ENCyclopaedia Of Dna Elements), which aims to find all functional elements hidden within the presumed ‘junk’. These findings suggested that more than half of the genome is transcribed into messenger RNA (see transcription) and that there are many previously unrecognized regulatory and other functional elements within the junk DNA.