Sunday, May 11, 2014

The Case for Junk DNA


With the advent of deep sequencing technologies and the ability to analyze whole genome sequences and transcriptomes, there has been a growing interest in exploring putative functions of the very large fraction of the genome that is commonly referred to as “junk DNA.” Whereas this is an issue of considerable importance in genome biology, there is an unfortunate tendency for researchers and science writers to proclaim the demise of junk DNA on a regular basis without properly addressing some of the fundamental issues that first led to the rise of the concept. In this review, we provide an overview of the major arguments that have been presented in support of the notion that a large portion of most eukaryotic genomes lacks an organism-level function. Some of these are based on observations or basic genetic principles that are decades old, whereas others stem from new knowledge regarding molecular processes such as transcription and gene regulation.

Concluding Remarks

For decades, there has been considerable interest in determining what role, if any, the majority of the DNA in eukaryotic genomes plays in organismal development and physiology. The ENCODE data are only the most recent contribution to a long-standing research program that has sought to address this issue. However, evidence casting doubt that most of the human genome possesses a functional role has existed for some time. This is not to say that none of the nonprotein-coding majority of the genome is functional—examples of functional noncoding sequences have been known for more than half a century, and even the earliest proponents of “junk DNA” and “selfish DNA” predicted that further examples would be found. Nevertheless, they also pointed out that evolutionary considerations, information regarding genome size diversity, and knowledge about the origins and features of genomic components do not support the notion that all of the DNA must have a function by virtue of its mere existence. Nothing in the recent research or commentary on the subject has challenged these observations.

- Read rest of the paper here

No comments: