Genes are Useful

A Caenorhabditis elegansA paper from way back in February, called The Majority of Animal Genes Are Required for Wild-Type Fitness (pdf), opened with the following:

Almost all eukaryotic genes are conserved, suggesting that they have essential functions.

What this jargon-filled sentence means is that “almost all” genes in animals/plants/fungi/protists exist in other animals/plants/fungi/protists (and sometimes even in bacteria), and have thus not been lost or otherwise discarded, which suggests that they are probably fairly useful. It’s worth realising here and now that this logic is based on the unspoken premise of evolution, which in sane-people land is a fairly safe assumption for research purposes. If creationism were true, on the other hand, there would be no basis upon which to draw such a conclusion. And it seems that the creationists should have been celebrating, because as the paper goes on to say:

However, only a minority of genes have detectable loss-of-function phenotypes in experimental assays, and multiple theories have been proposed to explain this discrepancy.

It’s too late for that party now, though. It turns out that these previous tests that came to the conclusion that only a minority of genes were important only looked at their immediate effects on the organisms they had in front of them. This new study looked at the longer-term impact on nematodes (specifically, C. elegans) that had certain genes artificially silenced, examining the changes in the rate of population growth over multiple generations. Lo and behold, worms with silenced genes left fewer descendants than the control. Case closed then: natural selection is indeed operating to protect these genes, and they are actually useful (somehow).

Except, for reasons unknown, Dr Jeffrey Tomkins has taken the time to dredge up this old paper and write an article called Gene Networks Are Intolerant of Mutation. The important part is the following:

The researchers wrote,

In contrast to previous estimates, we find that, in these multigeneration population assays, the majority of genes affect fitness, and this suggests that genetic networks are not robust to mutation. Our results demonstrate that, in a single environmental condition, most animal genes play essential roles.

In the biological evolution model, the process of genome mutation not only involves the hypothetical alteration of gene sequences, but the idea that not all genes are essential to life. In other words, there is room in the cell system for DNA to randomly change, so that once in a while it can spit out some useful new gene sequence to advance evolutionary progress. However, this new study shows that even though the cell systems in roundworms are dynamic and environmentally responsive, the fine-tuned DNA-based informational system that underlies it cannot be corrupted without diminishing its ability to survive.

So far as I know, the “biological evolution model” does not demand that “not all genes are essential to life.” It does, however, demand that “there is room in the cell system for DNA to randomly change,” but the evidence seems to be in favour of this being the case. Take the mutations study from last week, or Lenski’s E. coli experiment. Long-term effects of completely silencing a gene are one thing, but they don’t mean that the genes themselves cannot mutate and duplicate. And then, of course, we have the “junk” DNA, which quite definitely does have the ability to change its sequence without major adverse effects. Tomkins is wrong: genetic material can indeed be “corrupted”… if that’s how you choose to look at it.



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