Hacker News Reader

Comment by im3w1l | Hacker News Reader

In order to evolve there has to be some kind of genetic information passed on to descendants. But for prions there is no such mechanism. A lower energy state is assumed and that's that.

View on HN

There does not have to be genetic information for evolution.

Evolution only requires "descent with modification". DNA is a mechanism for this, but it is not necessarily the only one.

And prions don't have descent with modification. It's a regular mammal brain protein that got accidentally constructed backwards. There's nothing to pass on, nothing to modify.

Err, I think I remember a couple pretty famous articles that contradicts that prions generally don't have descent with modification, which may be what the person above us is referring to:

https://pubmed.ncbi.nlm.nih.gov/20044542/

https://pubmed.ncbi.nlm.nih.gov/17142317/

That's really neat. Still there should be a limited number of possible variants right? Like the energy landscape is fixed and will only admit so many possibilities?

FWIW Wikipedia says:

> Prion replication is subject to epimutation and natural selection just as for other forms of replication, and their structure varies slightly between species.[19]

[19] is https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848070

descent without modification sounds pretty hard to achieve for all but the simplest things.

This got me wondering: what is the advantage of genetic information (DNA / RNA) over a self-replicating entity without those convenient molecules?

My impression is that DNA / RNA-based organisms have a high tolerance for changes to their DNA / RNA, such that many genetic changes won't cause them to lose their self-replicating ability. This is great for evolution.

Prions, on the other hand, seem like they would have a low reproductive tolerance for changes to their structure.

So prions are simply a result of entropy? Am I understanding that correctly?

All evolutionary change (and life itself) is due a combination of differences of entropy (aka an energy gradient existing), combined with randomness in the current environment allowing mutation/change and hence selection pressure.

I would say life is an artifact of non-erodicity. Rare things that self-replicate are over-abundant in hindsight.

Reply on news.ycombinator.com