A 2015 New York Time science article on junk DNA* starts off by summarizing the test results for the DNA size of an onion vs. that of the NYT’s reporter’s: the onion is five times larger. Why is this so? Researcher summarizes the finding that has become accepted reality: that the size of an animal’s or plant’s genome has essentially no relationship to its complexity.
In the past, all of the “extra” DNA was considered to be junk. But today, researchers are coming to the view that noncoding DNA (the so call “junk”) seem to be as important to our survival as the DNA genes that encode proteins. Zimmer quotes Francis Collins, the director of the National Institutes of Health, January comment, “Most of the DNA that scientists once thought was just taking up space in the genome ‘turns out to be doing stuff.'” Zimmer’s article is mostly about the “the junk DNA wars are being waged at the frontiers of biology.” The history that Zimmer overviews is fascinating, and he gives the reader an historical account of this ongoing “war.” In one respect is is a battle about the correctness of the natural selection role in evolutionary biology.
An example is when he writes, “Scientists have long known that the human genome contains some genes for other types of RNA: strands of bases that carry out other jobs in the cell, like helping to weld together the building blocks of proteins.” This is how the fetus develops our structure from the limited amount of DNA genes.
Zimmer gives example from John Rinn from Harvard who did extensive research on an RNA molecule that, “somewhat bizarrely, was produced widely by skin cells below the waist but not above.” Rinn found that this molecule (he call it “hotair”) stuck to a protein called Polycomb that “turn genes on and off in different patterns, so that a uniform clump of cells can give rise to bone, muscle and brain.” Rinn contributions are summarized by Zimmer as follows, “there are thousands of RNA molecules encoded in our genomes that perform similar feats: bending DNA, unspooling it, bringing it in contact with certain proteins and otherwise endowing it with a versatility it would lack on its own.” DNA researchers talking about “folding” of genes in a manner similar to how we create 3-D structures by folding paper in different ways.
Another researcher, Alex Palazzo (a biochemist at the University of Toronto) writes, ““Much of what has been called ‘junk DNA’ in the human genome is actually a massive control panel with millions of switches regulating the activity of our genes.”
This is a fascinating article that I encourage you to read so that you can understand what is happening at the frontiers of evolutionary biology research, especially in the ongoing “DNA war.”
*Carl Zimmer, “Is Most of Our DNA Garbage?” March 5, 2015 NY Times Mag