From Uncommon Descent. The interviewer is science journalist Denyse O’Leary.
What caused the change of view about junk DNA? Can you suggest a couple of key findings?
In a word, evidence. The first to emerge was the fact that almost all of an organism’s DNA is transcribed into RNA. (So although most of it may be non-protein-coding, it codes for RNA.) From a Darwinian perspective, this is surprising: Why would an organism struggling to survive devote so many of its internal resources to producing supposedly useless RNA? Indeed, since 2003 it has become clear that non-protein-coding RNAs perform many essential functions in living cells.
Pseudogenes constitute one type of so-called “junk DNA.” These are segments of DNA that resemble segments that elsewhere (or in other organisms) code for protein. Yet RNAs transcribed from some pseudogenes have been found to function in regulating how much protein is produced by the DNA segments they resemble. Repetitive DNA, in which a non-protein-coding sequence is repeated many times, is another type of so-called “junk DNA.” Yet repetitive DNA is now known to regulate many essential functions, including embryo implantation in mammals.
There is also growing evidence that non-protein-coding DNA can perform functions that are independent of its sequence. One example is the region of a chromosome (called a “centromere”) that attaches it to other structures in the cell. Another example is the retina in the eyes of nocturnal mammals, in which non-protein-coding DNA acts like a liquid crystal to focus scarce rays of light.
Some claim that ID theorists predicted the finding and others claim they didn’t. What’s your take?
The literature doesn’t lie. Design theorist William A. Dembski wrote in 2004, “For years now evolutionary biologists have told us that the bulk of genomes is junk and that this is due to the sloppiness of the evolutionary process. That is now changing. For instance, researchers at the University of California at San Diego are finding that long stretches of seemingly barren DNA sequences may form a new class of noncoding RNA genes scattered, perhaps densely, throughout animal genomes. Design theorists should be at the forefront in unpacking the information contained within biological systems.” (The Design Revolution, p. 317.) At the time, biologists such as Dawkins, Coyne, Avise and Collins were still claiming that most of our DNA is junk.
Last week there was a paper in the peer-reviewed journal Science that discussed the problem of genetic similarities in different organisms that do not share a common inheritance. Evolution News talked about that here.