Talk:Mutationism

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This article seems to focus more on the idea that mutation is unimportant in evolution, introducing various errors and confusions on this subject, than on the stated topic of the article, which is mutationism. I just removed the erroneous claim that "mutation-selection balance" removes deleterious alleles from the population (after filling in the wikipedia stub on "mutation-selection balance"). In the current remaining text, the statement "levels of mutation necessary to cause significant evolution were not present in the environment and would cause sterility; e.g., in fruit flies" cannot be interpreted literally. It speaks of "levels of mutation" being "in the environment", but this is not where levels of mutation are. It suggests that if the "level" of mutation is high enough, this could cause "significant evolution", which may or may not be true, but is irrelevant, because this is not what mutationism proposes. The mutationists were the founding fathers of genetics, who toiled for years in the lab to find those rare mutations, so they were perfectly at home with the idea that mutations are rare.

I am an expert on this particular topic, and I thought that letting people like me fill in the details was what wikipedia is all about. I have tried to correct these mistakes in the past, including quotations to document what the mutationists *actually wrote*, but someone keeps reverting it. Will that person please explain what he or she is up to here, and what are his or her sources?

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I also think the article is both incomplete and incorrect. It does not distinguish between very different form of mutationism, and while it is not currently the main theory about molecular evolution, mutationism is alive and well, it's quite harsh to say it's discredited. Also, about creationism, isn't there a page for discussing creationist "arguments", we cannot refute their argument in every article about evolution, I'm not sure it's a good article to discuss such matter. -PhDP 05:08, 24 January 2006 (UTC)

[edit] UV and GC content

I have updated the claim by Singer and Ames that a high G+C content could be selectively advantageous with a new reference to Palmeira et al. (2006) Jean R. Lobry 20:05, 3 January 2007 (UTC)

[edit] Question: chromosome change?

I can't find an answer to this question, and thought I would post it here: How do chromosome numbers change? Say a population of a given species, all of which share the same chromosome number, is isolated from the main population. Time goes by. Now the chromosome numbers are different in the two populations. Does that happen? If so, how? By what mechanisms? --Serge 23:48, 6 December 2005 (UTC)

Short answer; Polyploidy. There's a very good book on the subject of genome evolution (including the evolution of chromosome number); The Evolution of the Genome by T. Ryan Gregory. You can google Polyploidy I'm pretty sure you'll find plenty of informations on the subject, mostly for plants. --PhDP 07:03, 24 January 2006 (UTC)

[edit] Removal of claimed "nonsense"

I removed the following sentence:

It was also demonstrated that levels of mutation necessary to cause significant evolution were not present in the environment and would cause sterility; e.g., in fruit flies.

This sentence does not make sense and does not make reference to any recognizable facts. It refers to "levels of mutation . . . present in the environment", but mutation is not present in the environment, it is a process within organisms. By referring to sterility and fruit flies, the statement makes it sound like it is based on some specific experimental result. If so, what is the result? What is the reference?

Yes. You irradiate fruit flies to produce mutations. It's quicker than waiting for them to happen naturally. You give them too much juice and they can't get it on. As for a reference, it's really at the level of common knowledge, but you might try to find something by Thomas Hunt Morgan, probably early 1930s. — Dunc|☺ 17:30, 19 May 2006 (UTC)

Here you are referring to levels of radiation to which the flies are exposed, but the disputed statement refers nonsensically to "levels of mutation . . . in the environment". As I said, mutation is not "in the environment". It is an internal process. Mutation is not the same as damage induced by radiation, oxidation, etc: damage is not heritable, but mutations (by definition) are heritable changes. For instance, a TT photodimer is damage, not a mutation; a broken strand is not heritable, but if error-prone repair of the strand introduces nucleotide changes, this represents a mutation.

But just putting the process of mutation back inside the organisms where it belongs would not fix the flawed logic. What principle of mutationism conflicts with the observation that levels of radiation sufficient to produce artificially high levels of mutation (levels that you admit are unnatural) cause sterility in flies? I see no contradiction. Neither apparently did Thomas Hunt Morgan, the mutationist and founder of genetics whom you cite as a source.

I agree with Dabs (who should sign his name using ~~~~). This part is ambiguous. It shouldn't be removed, but at least clearly explained. -PhDP 02:48, 20 May 2006 (UTC)

It makes perfect sense. The frequency of mutations required to cause significant evolution is far more than an organism can sustain, as demonstrated by the fact that if you artificially increase the frequency of mutations to that level, you get sterility. Now improve the wording, find a reference if you feel you need to, but don't remove it because you can't understand it. — Dunc|☺ 10:17, 20 May 2006 (UTC)

To make sense here, this argument would have to relate to mutationism, i.e., the view of De Vries and (in a later form) Bateson, Punnett, Morgan, etc. The argument seems to have three parts: 1) there is some level of mutation L "required to cause significant evolution"; 2) when the level of mutation is increased beyond L, sterility results; and 3) this somehow contradicts mutationism without contradicting other theories that erly on mutation. You have only addressed #2 (incompletely). How have you determined the level of mutation "required to cause significant evolution"? How does it relate to mutationism? De Vries found *actual cases* in Oenothera in which distinctive true-breeding forms arise in a single step that he called "mutation". De Vries's theory of evolution invoked this process and subsequent selection (i.e., De Vries was a radical species-selectionist: he doubted that within-species variation and selection could account for adaptation and diversity). Doesn't that vitiate the argument that the mutation rate is too low in nature? Later mutationists, such as Punnett and Morgan, did not accept De Vries's view, and invoked "gene mutations" as opposed to the kinds of chromosomal rearrangements common in Oenothera. However, in neither case is there a requirement for a high rate of parallel mutations to cause a mass conversion of the population from one form to another. This argument does not belong here, but perhaps in the entry on Ernst Mayr or Straw Man. --Dabs 12:48, 22 May 2006 (UTC)