Mutation bias reflects natural selection in Arabidopsis thaliana

I take this to mean that DNA repair mechanisms are more active in sensitive critical regions, and less active where potentially beneficial mutations can be tolerated?

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Yes it seems to be in some sense the reverse of somatic hypermutation. Rather than have particular regions targeted for high rates of mutation by enzymes that make mutations occur, some genomic regions are instead much more protected against mutation by different protective mechanisms.

Of course the finding that mutations are not distributed with equal probability across the genome as a whole, and that there are mutational hot spots and cold spots, has been known for a long time now.
Does a bias in a probability distribution make the process non-random? Mutations still appear to occur everywhere, just with unequal frequency, so in some places more than others. And in places with critical and house-keeping genes they’re more protected.

That doesn’t seem to me to substantiate any claim that mutations are directed to be more adaptive(as if the organism knows what kinds of mutations will be adaptive), since the organism can’t know whether mutations in a house-keeping gene might turn out to be adaptive in some future circumstance. This biasing of mutations to be lower in some regions is analogous to an adaptive, but ultimately still probabilistic behavioral strategy. Act in a certain way because this has in the past, on average, been less likely to be detrimental.

So no, I don’t think this is actually “challenging the prevailing paradigm that mutation is a directionless force in evolution.” It looks like textbook evolutionary game-theory, but with mutation biases instead of behavior.


Somatic hypermutation is not that particular wrt mutagenesis itself. The complexity of it shows how evolution cobbled it together. Mutation is selectively increased in highly expressed genes (transcription is literally required) in general, but mutations are not being repaired as often in the immunoglobulin genes. Thus the latter is a refinement layered upon the former, which still had adaptive value on its own. That’s still an oversimplification, because IIRC only one of the two major repair pathways is dialed down.

Exactly. They’ve never been alleged to be random in any other way, except by creationists looking to pummel a straw man.


Did you mean decreased?

No, I mean increased. I’m talking about somatic hypermutation in B-cell maturation. It’s one of the main reasons why we can get boosters of the same COVID vaccine that manage to increase our immunity to variants. The larger point that @Rumraket was making is that mutation rates can be dialed up as well as down.


A stupid-statistician question. It’s a professional hazard. :exploding_head:

Not stupid at all, thanks for asking.

I see so many different topic that I sometimes need to ask very simple questions to confirm my understanding. Sometimes it goes the other way - once ask if sex was an important analysis variable on a survey of pregnant teenagers. Doh!


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