Junk DNA, that vast genetic wasteland of seemingly useless biological rubbish may not be such a waste of space after all. New research suggests that it has some function, and the purpose of junk DNA may have helped distinguish humans from other species.
Finding the Purpose of Junk DNA
Over the years junk DNA has been given a bad wrap as a useless part of the genome. The simplest definition of the function of DNA is to produce proteins. Yet for many years junk DNA appeared to be without any discernible functions.
However, Japanese researchers from the Genome Institute of Singapore (GIS) have used gene sequencing technology to show that there's much more to junk DNA than meets the eye.
Gene sequencing and junk DNA
Junk DNA consists of many repetitive elements. Junk DNA consists of many repetitive elements. Using the latest gene sequencing technology scientists were able to show that 18-33% of the binding sites of five transcription factors, the proteins that control gene expression, are embedded in repetitive regions.
These transcription factors had roles in cancer and stem cell biology and throughout evolution these regions (and the transcription factors) were dispersed into other species. The researchers believe that it's likely that the genes that these transcription factors control differ from species to species. And that this could have created differences between species. Therefore they wonder how these can be regions of junk DNA when it appears they could have been major drivers in evolution, in helping to create distinctions between species.
What Purpose does Junk DNA Serve in Evolution?
It's been a widely held belief for some time now that evolutionary change in body patterns i.e. why a cat is different from a dog and a mouse looks nothing like a man, is due to the regulation of expression of genes; that is when and where they are expressed in the body and what sparks this burst of genetic activity.
It appears from this research that the key to this (which starts in the junk DNA) is that chunks of DNA housing binding sites for regulatory proteins can move around the genome and alter the activity of their new neighbours, the genes next to where they end up.
The research was published in the November 4th 2008 edition of Genome Research and sparked renewed research efforts on at least two fronts. One is to continue to probe junk DNA looking for any signs of functionality and the other is to focus more on the genetic basis of changing body patterns over evolutionary time. One wonders how much longer the term 'junk DNA' will be in use for. Surely its days are numbered?