 |
Figure 1. Summary of haploid nuclear DNA contents (“genome sizes”) for various groups of eukaryotes. This graph is based on data for about 10,000 species [18], [19]. There is a wide range in genome sizes even among developmentally similar species, and there is no correspondence between genome size and general organism complexity. Humans, which have an average-sized genome for a mammal, are indicated by a star. Note the logarithmic scale.
|
The Case for Junk DNA
Overview
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....
For full story see the free access full paper at PLoS @ PLOS Genetics: The Case for Junk DNA:
...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.
Citation: Palazzo AF, Gregory TR (2014) The Case for Junk DNA. PLoS Genet 10(5): e1004351. doi:10.1371/journal.pgen.1004351
Published: May 8, 2014
Copyright: © 2014 Palazzo, Gregory. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
For the rest of us, Carl Zimmer, as always, does a great job on this topic:
Genomes are like books of life. But until recently, their covers were locked. Finally we can now open the books and page through them. But we only have a modest understanding of what we’re actually seeing. We are still not sure how much our genome encodes information that is important to our survival, and how much is just garbled padding.
Today is a good day to dip into the debate over what the genome is made of, thanks to the publication of an interesting commentary from Alex Palazzo and Ryan Gregory in PLOS Genetics. It’s called “The Case for Junk DNA.”
The debate over the genome can get dizzying. I find the best antidote to the vertigo is a little history. This history starts in the early 1900s.
At the time, geneticists knew that we carry genes–factors passed down from parents to offspring that influence our bodies–but they didn’t know what genes were made of.
That changed starting in the 1950s. Scientists recognized that genes were made of DNA, and then figured out how the genes shape our biology...
H/T to +Mike Lewinski
No comments:
Post a Comment