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A new study finds that most "silent" mutations are harmful rather than neutral:
Marshall Nirenberg, a University of Michigan alumni, and a small group of researchers cracked the genetic code of life in the early 1960s, figuring out the rule by which information stored in DNA molecules is converted into proteins, the functional components of living cells.
They discovered three-letter DNA units called codons that describe each of the 20 amino acids that make up proteins. This discovery would win Nirenberg and two others the Nobel Prize.
Occasionally, single-letter misspellings in the genetic code, known as point mutations, occur. Nonsynonymous mutations are point modifications that alter the protein sequences that result from them, while silent or synonymous mutations do not change the protein sequences.
[...] “Since the genetic code was solved in the 1960s, synonymous mutations have been generally thought to be benign. We now show that this belief is false,” said study senior author Jianzhi “George” Zhang, the Marshall W. Nirenberg Collegiate Professor in the U-M Department of Ecology and Evolutionary Biology.
“Because many biological conclusions rely on the presumption that synonymous mutations are neutral, its invalidation has broad implications. For example, synonymous mutations are generally ignored in the study of disease-causing mutations, but they might be an underappreciated and common mechanism.”
[...] Zhang said the researchers knew beforehand, based on the anecdotal reports, that some synonymous mutations would likely turn out to be nonneutral.
“But we were shocked by the large number of such mutations,” he said. “Our results imply that synonymous mutations are nearly as important as nonsynonymous mutations in causing disease and call for strengthened effort in predicting and identifying pathogenic synonymous mutations.”
The U-M-led team said that while there is no particular reason why their results would be restricted to yeast, confirmations in diverse organisms are required to verify the generality of their findings.
Reference: “Synonymous mutations in representative yeast genes are mostly strongly non-neutral” by Xukang Shen, Siliang Song, Chuan Li, and Jianzhi Zhang, 8 June 2022, Nature. DOI: 10.1038/s41586-022-04823-w
(Score: 3, Informative) by bloodnok on Monday August 29 2022, @06:49PM (2 children)
You're missing the power of natural selection. If a mutation is, or becomes, harmful your chances of having successful progeny are reduced. Harmful mutations are mostly selected against.
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The major
(Score: 2) by Common Joe on Tuesday August 30 2022, @02:34AM (1 child)
I wasn't trying to fully define our current understanding of evolution. (I wouldn't be qualified anyway.) And my point wasn't about harmful vs beneficial mutations. You're correct in that evolution of an organism depends upon its environment. (It's the environment which defines whether a mutation is harmful or not.)
My point is purely a thought experiment (because it can't exist in the real world): If the environment is neutral towards an organism, and the organism can survive with it's neutral mutation, the net result is that it's easier for a mutation to de-evolve than to evolve. An example: It's easier to de-evolve an eyeball rather than to create one through purely random mutations. A "monkeys writing Shakespeare" kind of thing. Because of this, all organisms would de-evolve in the long run. Bigger organisms would lose the ability to see, hear, taste, etc. Smaller organisms like cells would simply lose the ability to hold themselves together.
(Score: 2) by Common Joe on Tuesday August 30 2022, @03:06AM
Ugh. Forgive me. I'm really tired. It looks like I just argued against myself. But both of my comments can still fit together, though. And now I'll try to address your comment, bloodnok.
In a neutral environment, we would de-evolve... into nothing. I'll rephrase this: Most mutations are harmful in a neutral environment which is achieved only in a thought experiment.
But we aren't in a neutral environment. We're in a closed environment. If evolution was more harmful, we wouldn't have life on this planet at all; if life were dropped on a planet in a neutral environment, it would de-evolve. Things like eyeballs would go away and cells would eventually go away too. Thus, it's pretty clear that evolution (which takes into account the environment) is not harmful to life. Evolution pushes changes in a net positive direction for a given environment, but that environment changes as soon as you get that new organism with that new mutation.
You know what, I don't feel I'm making any sense here nor converging on any point I want to make. It seems my ability to respond to your comment just falls flat. Unfortunately, I can't go back to sleep either because I have to get ready for work. I'll just give up and pretend to be awake at my work environment. I hope my mutations allow me to be more coherent there so no one notices I'm asleep.