Success rate of mutations:

[CP489]

A friend and I were talking about evolution and he mentioned that the success rate of mutations is less than .1%. He "didn't remember" where he got this tidbit, but I'm wondering if it's even relevant. Since you guys are generally more educated on such things than myself, I figured I would ask all of you.


I had mentioned that those with beneficial mutations were more likely to reproduce, thereby passing on the mutation, in case you're wondering about the context.

So did I misrepresent something, did he, or is any of this even relevant.

Thanks in advance.

 

[Roboramma]

A friend and I were talking about evolution and he mentioned that the success rate of mutations is less than .1%.

Well, I'm no expert, so take this all with a grain of salt, but I don't really even know what that would mean.

I mean, most living things are very well adapted to their current environments, so we'd expect that any mutation would tend to either do nothing, or make them less well adapted. Similarly, if I were to take a straight flush in poker and replace some of the cards at random, likely you'd have a worse hand.
On the other hand, it's possible that the hand could be improved (just unlikely).

Now what happens when the environment changes (and this is happening all the time, particularly with respect to the living part of the environment that's evolving along side you). You're previously well adapted body might not be so well adapted any more, and those mutations that might not have been beneficial, will be.
Similarly, if you had that straight flush, and we suddenly decided that we were playing a different game, or to tweak the rules slightly, a random change to one or two cards in your hand might give you a big benefit.

What I'm getting at is that the likelihood that a mutation will be beneficial should tend to change with the circumstances, and with the organisms that we're talking about.
So I don't know where the number could really come from (though someone else might be able to justify it). I can see that it would make sense as an average for all life on earth throughout it's history, but how anyone could have calculated that average, I can't imagine.
Maybe it's something like - of all the mutations we've observed in the laboratory, 0.1% have turned out to be beneficial. That would be a meaningful number, I guess.

Hm...

 

[Soapy Sam]

Like Roboramma , I think the statement " the success rate of mutations is less than .1%. " is meaningless.
Define " success" for a start.
Define " mutation" . Most mutation occurs in somatic cells rather than germ cells, because somatic cells are vastly more numerous. Are we to restrict the comment only to germ cells?
Is a mutation which causes a cell to become cancerous and reproduce uncontrollably "successful" or not? It is for the cell- at least until the host dies.
I'd say your friend needs to do a lot more reading.

 

[Anacoluthon64]

Define " success" for a start.

Aye, there's the rub. It seems we can only decide its value after the fact, i.e. in terms of continued survival, and even then it may alter. Moreover, there's the question of whether "success" is binary, i.e. yes/no, or can degrees of success be ascribed? How do we count the unsuccessful ones (or just estimate their number) that have disappeared without any trace? Is an erstwhile success that has become extinct through a change in environment or habitat still a success?

As an instructive though perhaps contrived example, consider a giraffe's environment invaded by a variety of insect that begins denuding only tall trees of their foliage. The giraffe's long neck will become a decided disadvantage, whereas previously it was just the opposite. Whither "success" now?

'Luthon64

 

[Dr Adequate]

A friend and I were talking about evolution and he mentioned that the success rate of mutations is less than .1%. He "didn't remember" where he got this tidbit, but I'm wondering if it's even relevant. Since you guys are generally more educated on such things than myself, I figured I would ask all of you.


I had mentioned that those with beneficial mutations were more likely to reproduce, thereby passing on the mutation, in case you're wondering about the context.

So did I misrepresent something, did he, or is any of this even relevant.

Thanks in advance.

You may find the article [swiki]Mutation[/swiki] of interest.

As for his figure, if, by "success rate" he means the proportion of mutations that are beneficial to the organism, then let's do the maths. Multiply 0.001 through by the hundreds of mutations (differences from the parental genome) that each organism in a gene pool gets in its germ line. Multiply this through by the thousands or millions of individuals in the gene pool. Realize that if his figure is correct, several beneficial mutations enter the gene pool of every species in every generation.

He probably fails to appreciate that the good mutations are selected for by natural selection (creationists don't know about natural selection) and the bad ones selected against: so the relatively small number of good mutations doesn't stop them from winning out over the bad ones.

 

[Dr Adequate]

Aye, there's the rub. It seems we can only decide its value after the fact, i.e. in terms of continued survival...

No.

For example, company X intends to introduce a new anti-streptococcal antibiotic, Y.

Question for the reader : in which organisms will mutations having which effect be beneficial?

 

[Paul C. Anagnostopoulos]

As Dr. A says, .001 "good" mutations is just marvelous.

Now, how about "bad" mutations? Creationists love to point out that almost all mutations are bad. I think we are beginning to learn that most mutations are neutral.

~~ Paul

 

[Anacoluthon64]

No.

For example, company X intends to introduce a new anti-streptococcal antibiotic, Y.

Question for the reader : in which organisms will mutations having which effect be beneficial?

Point taken, although I took it as understood that highlighting the subjectivity of "success" was Soapy Sam's main thrust in the post I quoted. That is why I neglected to reemphasise the point, and instead raised peripheral and perhaps somewhat less obvious issues.

'Luthon64

 

[Soapy Sam]

In case anyone looking in does not get Dr.A's point.

A mutation imparting resistance to the new antibiotic will be beneficial to the bacteria and harmful to humans in general and stockholders in company X in particular.

Note that even without any mutation occurring in the present population of the bacterium, some individual bacteria will be more innately resistant than others. If some of these survive the treatment, they will multiply (because most of their competition has just been conveniently removed). They will also pass on their resistance to less resistant new arrivals via plasmid (DNA ) exchange, which is a sort of non-reproductive sex bacteria engage in. (No, it's not just primates and cetaceans)

Mutation is only one of many evolutionary mechanisms.

And Anacoluthon64 - yes, subjectivity was indeed my point.

 

[Dr Adequate]

Note that even without any mutation occurring in the present population of the bacterium, some individual bacteria will be more innately resistant than others...

Mutation is only one of many evolutionary mechanisms.

My underlining.

Of course the useful mutation is as likely to occur (over a given time period) before or after the introduction of the drug. 'Cos mutations are random. This random variation remains all that natural selection has as raw material to work with.

 

[Soapy Sam]

Gotcha. I was making the same point. If 1 bug survives in the present population it's because it is somehow different from the rest. Could be it acquired a new gene from it's ancestors, or laterally via a plasmid, but if you track that gene back far enough there's a mutation somewhere (or some recombinant equivalent in a sexual species).