Junk DNA … Really?

Update Sept 18, 2012: Recently an article was published in the Wall Street Journal that shows new and more profound uses for ‘Junk DNA’ a term we believe is no longer appropriate. Click here to read the full article.

There have been discussions surrounding so called ‘junk DNA’. What is it really? Can DNA really be considered junk and why was this term used to describe non-coding DNA? We at ConnectMyDNA™ wanted to dispel any rumors about what this truly is.

The term ‘Junk DNA’ was introduced in 1972 by Susumu Ohno, as a provisional label for the portions of a genome sequence for which no discernible function had been identified.

According to an article published in News Medical on Junk DNA, it states that “The term is currently, however, a somewhat outdated concept.”


We decided to dig deeper and go directly to a reliable source, Dr. Michael Baird to answer some specific questions about ‘non-coding’ or ‘junk DNA’. Dr. Baird has a PhD in genetics from the University of Chicago and was a Research Associate at Columbia University in the Department of Human Genetics and Medicine for 3 years after receiving his PhD. He published over 50 articles in peer review journals as well as chapters in books about the use of DNA for identification. He was the first to testify in a criminal trial involving DNA evidence and has since testified in over 350 criminal cases.

Q. Dr. Baird, what is ‘junk DNA’?

A. Junk DNA is a term that was developed more than a decade ago to describe regions of the DNA that do not have a coding function, and thus are not considered genes. A gene is a segment of DNA that that contains the coding information to make a protein required for a function. Only about 10% of our DNA falls into the category of gene. A decade or more ago, the term junk DNA was used to describe the 90% of non- gene material. Since that term was used, scientists have discovered that many of the regions thought to be junk DNA actually do have a role in gene expression as promoters, suppressors, or modifiers of gene activity. So, the term junk DNA is not used much today to take into account the many different ways DNA can be expressed.

Q. Does ‘junk DNA’ serve a purpose?

A. Regions of the DNA once considered as junk DNA have been shown in the last decade to have roles in gene regulation. Many scientists who study DNA feel that as knowledge is gained about how genes function, that more of the DNA will be demonstrated to have a function that was not apparent initially. The study of DNA function is a moving target and with more knowledge comes a new appreciation of how non-coding DNA segments can affect genes.

Q. Why would the 13 CODIS loci be considered as junk DNA when they are being used by forensic scientists for identification?

A. The moniker ‘junk DNA’ refers to the view that the loci examined are not considered genes in that they do not produce a protein. As indicated above, this viewpoint has changed over the last decade. The reason the term junk DNA was used is more a function of not knowing enough about DNA to understand regulatory functions. This does not necessarily mean that the CODIS loci will be shown at some time to have a function, but that can not be entirely ruled out.

Q. Given ConnectMyDNA Uses the 13 CODIS loci does this invalidate the test in any way or make it less legitimate because we are using what is being referred to as non-coding or ‘junk DNA’?

A. No. The 13 CODIS loci have been used by the FBI and law enforcement for more than a decade to convict the guilty and exonerate the innocent. It was fortunate that scientists discovered that such hyper variable loci exist in the human populations which allowed the development of powerful DNA identification systems. ConnectMyDNA™ goal is to provide you with information and give you the opportunity to decide how to use this information provided. Please visit our webs site to view this blog along with additional information on ConnectMyDNA™