CB130: “Junk” DNA is not really junk
[The following is only an excerpt from a recent post on Homologous Legs, the blog/website of the Young Australian Skeptic and Pseudo Scientist contributor Jack Scanlan.]
This is a post refuting part of the CreationWiki response to Talk.Origins’s “Index to Creationist Claims”. Click here for an introduction to this project. Quotes from CreationWiki are in red, while quotes from Talk.Origins are in blue.
So-called junk DNA is not really junk. Functions have been found for noncoding DNA which was previously thought to be junk, and we cannot be sure that the rest of the junk DNA is not functional as well
Okay, so let’s back up here. What does this claim mean, and how does it attempt to argue against evolution/for creationism?
The claim, as stated above, is that “junk DNA”, or non-coding DNA found in the genomes of organisms, has been found to have various functions in the cell, other than coding for proteins. This is true, and these functions are usually regulatory, involving coding not for proteins but for RNA strands that move around inside the cell and control various biochemical processes.
This ties into creationism and intelligent design, because proponents of these ideologies believe that the genomes of organisms were designed with purpose, so how can sections of DNA have no purpose at all? Such would not be the handiwork of an omnipotent and omniscient God.
You can probably see where I’m going with this. The junk DNA creationist claim is not about arguing for creationism or against evolution, it’s about responding to the anti-creationist claim that junk DNA offers strong evidence against a deity designing life. Because of this, Talk.Origins is responding to a response, and CreationWiki is responding to the Talk.Origins response. Confusing, eh?
It has long been known that some noncoding DNA has important functions. (This was known even before the phrase “junk DNA” was coined.) However, there is good evidence that much DNA has no function:
While it is true that noncoding DNA is long known to have important function [sic], that does not really affect the claim.
No, it doesn’t, but that was not the main point of what Talk.Origins was trying to say. In fact, you cut them off right before they were about to get to the important stuff, which you do, admittedly, address later. Oh well, on to what they actually say that has any meat to it.
Sections of DNA can be cut out or replaced with randomized sequences with no apparent effect on the organism (Nóbrega et al. 2004).
While this is a useful test, it can only determine if there is an active use for the “junk” DNA. For example, in a computer data center, one could cut out the entire backup system and replace it with randomized computers and it would have no apparent effect on the datacenter — that is until a restoration was needed.
So, what is CreationWiki saying here? That the non-active parts of the genome are analogous to a backup system? What evidence to they have for this, and does the analogy stand up? Er, none and no, respectively.
You can’t claim that a system has a certain function, or even any function at all, without having evidence that supports that. It is assumed that sections of DNA do nothing until we have evidence of what they do, not the other way around. To do the reverse would be an argument from ignorance, and this is essentially what CreationWiki is doing: ‘We don’t know what this DNA does, so it must have some sort of function that we don’t know about.’
The backup analogy fails because it simply doesn’t make sense, plus, you have the argument from ignorance rearing its head again: lack of evidence = our lame analogy. Wrong.
Likewise, in the creationist model, many regions of DNA are for adaptive purposes, and are not activated except in specific environments where they are needed. If this is indeed the case (and there is evidence that it is), this indicates design on quite a grand scale. If it can be shown that there exist adaptations within an organism for environments which the organism has never experienced that can be easily switched on reliably by the organism itself, that is significant evidence for design. The problem being that it is difficult to determine for certain the complete natural history of an organism and what proteins it had needed in the past.
CreationWiki gives no reference to this evidence they have for the genetic frontloading that they are claiming exists within the genomes of organisms. Of course, if such frontloading did exist, it would be great evidence for design, especially if the dormant systems were extremely complex, but you can’t jump to conclusions based upon what a creationist wiki said. Further data required, and the null hypothesis, that such frontloading does not exist, is supported until then.
In addition, modern experiments have shown that DNA can in fact spontaneously revert mutations back to the original coding. This indicates that there may be a repository that genes can use to verify the validity of their coding. In computers, memory cells can contain hamming codes which are extra memory cells to verify the integrity of other cells. This is not the same as a backup copy, and instead are parity bits — so an observer not aware of the coding would not necessarily be able to make out what it means. Cells apparently have some sort of mechanism like this in order to be able to revert mutations, and therefore it is not unreasonable to think that some of this “junk” DNA is in fact some sort of parity mechanism for other coding regions.
Yes, such genes do exist, but they don’t revert every mutation, and they certainly aren’t like a backup system. They also do not make up all of the junk DNA sequences, which CreationWiki rightly admits, so the original anti-creationist claim, that some DNA has no function, still stands.
Likewise, transposons have often been looked at as parasitic elements of DNA. This is based on the assumption of a static genome. In the creationist model, transposons are part of the genome’s mechanism for organizing itself. Evolutionists agree with the transposon’s role in speciation, but most still view them as only occurring by non-adaptive mechanisms, where there adaptiveness is a happenstance that is selected for, not a design quality.
Transposons, for those who don’t know, are like little moving bits of DNA that reside within our genomes. They contain within themselves the code for restriction enzymes that specifically target the base pair sequences that define the boundaries of the transposon, and this means that they can jump around inside a cell’s nucleus, disrupting genes and generally playing havok with the internal workings of the cell. It must be noted that transposons don’t always ruin genes when they insert themselves after a jump, as a matter of fact they usually don’t, and this is more evidence for the existence of non-functional DNA sequences within the genome.
But transposons as part of the genome’s “mechanism for organising itself”? I don’t think so. They don’t organise anything, they just stuff things up. Again, evidence needs to be provided for the claim made by CreationWiki, and they once again fail to deliver.
[To read the entire post, click here]