Talk:Muller's ratchet

message: The paragraph on RNA viruses is completely incorrect. The paper cited makes no mention of Muller or the ratchet effect; in fact, the authors of the paper theorize that it is the failure of the high-fidelity viruses to mutate around the host immune system. The paragraph in this page states that the wildtype high mutation rate allows reversion mutations to escape Muller's ratchet, but this is a fallacy, as a higher mutation rate, by Muller's definition, leads to more deleterious mutations than to reversions. A high mutation rate simply accelerates the ratchet effect. I am going to delete this paragraph in a few days, unless someone can come up with evidence that it should stay.
Estewar01 (talk) 18:57, 9 September 2016 (UTC)
thread_title: Untitled

message: I am not going to edit this page as I am already mentioned in it.  But in my opinion the Ratchet is not mentioned in Muller's 1932 paper.  I think the clearest way to think of this is that in that paper Muller did invoke what we now know as the Hill-Robertson effect, the interaction of selection and drift at closely linked loci that interferes with response to selection.  This was the basis of both Fisher's and Muller's theory of the advantage of recombination.  But the Ratchet, in which in the absence of recombination, the fittest class of haplotypes gets lost and can only be regenerated by back mutatiion (or immigration from elsewhere), is first mentioned in Muller's 1958 paper.  The followup to that paper also uses the word "ratchet" (as mentioned in this page).   Muller (1964) says that the population 
an asexual population incorporates a kind of ratchet mechanism, such that it can never get to contain in any of its lines, a load of mutation smaller than that already existing in its present least-loaded lines.
Muller's Ratchet was pointed out to me by Jim Crow which led to me working on it after I began to understand the Hill-Robertson effect and saw that it was the overarching phenomenon that explained the Ratchet as well as the Fisher-Miller argument for the evolution of recombination. Felsenst (talk) 14:15, 7 November 2011 (UTC)
thread_title:  When the Ratchet was and wasn't introduced 

message: It seems that the ratchet only operates when 2 key conditions are met. (1) back-mutation is absent (or at least very rare in some undefined precise sense) and (2) the population is small so stochastic effects are important. No attempt is made in the article to justify these assumptions, except by references to technical books and articles. Maybe they are good assumptions justified by data, but neither are obviously true. A lay reader will gain the impression that asexually reproducing species will rapidly become extinct, which seems nonsense (even if these species do not exhibit extensive non-sexual recombination).
It's completely counterintuitive that the highest-fitness genotype will disappear and be replaced by lower-fitness genotypes, since by definition the highest fitness genotype is best at surviving and reproducing. But of course if the population is small and chance fluctuations are important, even the best genotype can be lost. The article needs to include that important "even",which aids understanding. It also needs to explain why back mutation is even less likely than these rare fluctuations that can remove the best genotype, which is not intuitively obvious. Paulhummerman (talk) 15:52, 26 October 2021 (UTC)
thread_title:  Clarifications Needed