Talk:Genetic drift

message: See also: Talk:Evolution/Genetic drift
Genetic drift looked at in the sense of modern day public policies we will find displaced genetics in new environments. Meanwhile, natural disasters also play a major role in modern day genetic drift. For example, communities must have low income housing making all neighborhoods accessible to all and not exclusive to one ethnicity or culture. This leads to resulting in procreation between genetics that may have never crossed paths, or in general, outside their normal community. As mentioned, natural disasters will displace individuals as well. In our modern time we have lived through wildfires, hurricanes and currently flooding and overall sinking in certain regions of the world. This uncontrollable events also lead people to migrate and settle in new environments. Adapting to new ways of life and ultimately new people. Ralle034 (talk) 18:44, 10 February 2022 (UTC)
thread_title: Untitled

message: Random sampling is clicked and it sends you to the statistical practice.   —Preceding unsigned comment added by 98.149.131.179 (talk) 23:02, 18 April 2010 (UTC)
replies: text: Theoretical Population Genetics by JS Gale (1990) p 13 uses two different terms for these two processes: "random genetic drift" and "random fluctuation in intensity of selection", but characterizes both of them as stochastic processes. Professor marginalia (talk) 20:46, 19 February 2009 (UTC)
replies: text: Gale calls "random genetic drift" "random genetic drift" and "stochastic changes in selection intensity" "random fluctuation in intensity of selection". So ... ? --Ettrig (talk) 21:24, 19 February 2009 (UTC)
replies: text: No, I meant he says there are (at least) two types of stochastic processes, random genetic drift and random fluctuation in intensity of selection--random genetic drift by Gale has the traditional meaning, ie random sampling of alleles.  But I found another source that treats it differently, I'm skimming it now.  Basically this one wants both to be considered genetic drift, along with other stochastic processes. I'll give its synopsis asap, but this looks like there is no "one view" of this yet.  It may require us to describe and attribute all representative views on this. It's clear even in the source I'm reading that genetic drift has a traditional definition (random sample error), and this book is pushing for a wider definition.  More soon. Professor marginalia (talk) 21:48, 19 February 2009 (UTC)

text: OK, here it is.  Another one, by Kimura (who I believe is one at the forefront of a new "revival" of drift in contemporary population genetics), Population Genetics, Molecular Evolution, and the Neutral Theory (1994) fills out some of the missing pieces.  The discussion requires some development here, I think, especially with better integration with the historical development and status of drift theory in the overall context of traditional evolutionary thought. In terms of evolutionary biology, I don't believe his views have taken firm hold yet, but his work is definitely influential, drawing a lot of interest and attention. In evolutionary thought you find a solid core of "selectionists" who will allow that drift plays only a minor role in evolution-and they've traditionally held to the "slow, gradual change guided by natural selection" model.  This view has been strong going all the way back to the early days of the modern synthesis, with probably R. A. Fisher its greatest influence.  Then you find a smaller number coming from different angles who push against the idea this is the best "standard model". What Kimura puts forth in this paper about drift is an argument of sorts to broaden the scope and consider how random processes factor beyond sampling error in small populations.  The traditional meaning of genetic drift was based on Wright's work and correlates to random sampling.  This Kimura calls "the narrow view".  He also disputes the traditional view that drift has little significance outside of small populations.  We really need more sources on this - but it would be good to cover the subject.  I'll see what else I can pull together.  Professor marginalia (talk) 22:27, 19 February 2009 (UTC)
replies: text: Maybe we should call it drift by random natural selection?  ;-)  --Ettrig (talk) 10:13, 21 February 2009 (UTC)
replies: text: Modern mathematical models of drift descend mostly from Kimura's work, which is entirely based on drift as a sampling phenomenon. Other usages might exist but I think they're marginal at best. Graft | talk 23:38, 16 March 2009 (UTC)
thread_title: Random sampling

message: I reworded the lead. It's still a little clumsy, but is better. Are there any defects? I'm thinking of rewriting the second paragraph to briefly explain the "four" in "genetic drift is one of the four processes" (mutation, drift, flow, natsel). If that can't be managed in the lead, it might be better to omit "four". Does anyone know of a good (simple) reference so we could just link it? There should be something in WP, but I can't find it. --Johnuniq (talk) 10:52, 24 February 2009 (UTC)
replies: text: I would rather remove "four" than add the list. The "four" was there because of a concern earlier that we give the impression that there are only two subprocesses. --Ettrig (talk) 11:21, 24 February 2009 (UTC)
replies: text: The lead sentence in Population genetics spells it out but it's not sourced there either.  I can find a source though--that won't be a problem.  I think for awhile the lead contrasted genetic drift (random change) to natural selection (adaptive evolution).  Then later it was changed to say there were two evolutionary mechanisms.  I think the natural selection comparison should be in the lead, and it shouldn't say there are two when there are four.  The article should talk about some of the models involving more than one mechanism along with genetic drift; for example, dynamic models with a mix of mutation, drift and gene flow.  Absent some discussion of the mix, there's not much to be said about all of the mechanisms in the lead.  These sentences bother me here, "The inter-generational changes are usually small, and genetic drift is usually slow, but in the long run drift can account for a large proportion of the changes in a gene pool. Genetic drift reduces genetic variability, and may cause gene variants to disappear completely."  What are "small changes"? What is meant by "slow changes" and "long run"?  Maybe it's all relative, but to me the changes look very sweeping and very rapid in genetic drift.  The mounting of slow change over a long time period is the classic natural selection model, not classic drift.  What are we saying there?  Professor marginalia (talk) 15:01, 24 February 2009 (UTC)
replies: text: I would change to "Genetic drift can account for a large proportion of the changes in a gene pool. It commonly causes gene variants to disappear completely and thereby reduces genetic variability." Please suggest or add a formulation about combined effects. --Ettrig (talk) 16:19, 24 February 2009 (UTC)

text: What it boils down to is population size. The smaller the population, the bigger and faster the changes can be.  Large populations don't budge much at all from drift, and most consider drift relevant only to small populations (one source defined n<200).  Ettrig may prefer to say drift is smaller and slower in large populations. Many sources I've seen treat drift as so unlikely in a large population, the odds so small it would occur in them, that it's not considered to have much relevance there.  These are largely probabilistic conclusions; there isn't much in the way of real world verification about what kinds of phenotypic evolutionary changes (such as the development of the eye) can be attributed to any one kind of mechanism.  But there is so much written about the issues they're looking at in evolutionary models of population change.  It would be very interesting, I agree, to include some of the issues and dilemmas in the article here. Professor marginalia (talk) 08:02, 25 February 2009 (UTC)
thread_title: Lead

message: The first sentence in the main text has the kind of explanation that I am asking for. A population's allele frequency is the fraction of the population's genes having a given allele variant. Unfortunately this formulation runs a high risk of being misinterpreted. The word population most often is interpreted as all the organisms somewhere. Here it refers to a set of gene copies. So if the allele is A, the only other allele is B, there are 5 organism individuals, one AA, two AB, two BB. Then the allele frequency of A is 40% with the correct definition. With the current definition it could very easily be interpreted as being 60%, three out of five organism units have allele A. --Ettrig (talk) 06:57, 22 March 2009 (UTC)
replies: text: Yes, you have a good point.  What about, "An allele frequency is a measurement of the frequency of a particular allele relative to the total number of alleles at that locus in a population."  The misunderstanding is compounded by the "for example" saying a frequency can't remain 50% going from an even numbered population to an odd numbered population, because of course even if population n is an odd number, 2n is an even number and you can still arrive at a clean 50% allele frequency mathematically. I don't like that example for other reasons also.  Professor marginalia (talk) 17:24, 22 March 2009 (UTC)
replies: text: I have argued at an enourmous length that frequency as used in population genetics is a technical concept that needs to be explained. In view, so is allele. So I would like the explanation not to use these words. "Genes often occur in variants, called alleles, with slightly different function. The fraction of all the gene copies that is made up of a particular variant is called its allele frequency."--Ettrig (talk) 17:45, 22 March 2009 (UTC)
replies: text: It was "population" that led to the possible misunderstanding, not "frequency".  Alleles are not required to have any function at all, and sometimes different alleles will share a given function in common.  Some of the most valuable findings come from analysis of those allele differences that are thought to have no associated function.  Why are we throwing this in? Professor marginalia (talk) 17:54, 22 March 2009 (UTC)
replies: text: Agreed on different function. This is not part of the concept of allele. (But it was for many decades.) Frequency is currently explained. You suggest that the explanation is removed. I ask that it is kept. I have argued extensively for this above, showing that textbook authors do. I have seen no valid counterargument. --Ettrig (talk) 21:43, 23 March 2009 (UTC)
replies: text: Here I quote again from the Dictionary of Science, "gene frequency-the relative frequency with which a particular gene is present in a particular population of a species or other group".  Professor marginalia (talk) 23:21, 23 March 2009 (UTC)

text: This is a specialist topic. Requiring readers to understand what 'allele' is before they read it is not a high bar. It's linked in the first sentence. It's used throughout the article. If you don't know what 'allele' means, you shouldn't be reading this thing. Your habit of wanting to "explain" by removing indispensable terminology seems wrong to me. Graft | talk 18:15, 23 March 2009 (UTC)
replies: text: We have different opinions on what should be explained. In the case of frequency I have backed mine by pointing out that textbooks do. That is, I have presented a valid Wikipedia argument. You have not. Specialist topic is definitely not a valid Wikipedia argument. I have pointed out the Wikipedia standard of accessibility above. I did not remove the word allele earlier, except for the very first sentences. My line is that the first 1-3 sentences should be without allele, frequency and sampling. Then these words should be explained, then used. --Ettrig (talk) 21:43, 23 March 2009 (UTC)
replies: text: I agree with graft.  If a reader doesn't know what an allele is, there is no reason to explain genetic drift in "simple" terms to them.  "Allele" isn't the hitch, "frequency" isn't the hitch.  Genetic drift is a particular evolutionary mechanism-are we going to explain evolution? No, this isn't an introductory class in biology and genetics, it's an article about drift.  So what is drift? It's a purely random change in allele frequency.  It's very different than "natural selection".  What do we mean "random"? In genetic drift, it's very different than "random mutation".  In drift, it's the "random sampling" of existing alleles during reproduction. As in random mating within the population, random environmental episodes which impact individual survival and reproduction, random isolation/removal from the ancestral population, etc. Who "discovered" it? How do they measure/estimate it?  What impact can/does drift have in evolution? What are some real examples of it? How are drift models used in research in population genetics? That's it! It's about drift. Drift. Drift. I think we should leave off worrying about explaining what an allele is to the allele article, and let's focus on explaining drift as best we can.  For further support, I offer yet another source-The American Heritage Dictionary of Science, touted on the flap as "bridging the gap between overly simplified and the highly technical": "the fluctuation in gene frequency occurring in an isolated population, presumably due to random variations from generation to generation." There is no term more fitting than "frequency", if for no other reason than that's what it is and what it's called. Professor marginalia (talk) 22:17, 23 March 2009 (UTC)

text: In a population of organisms, several different alleles may occur at a particular locus. Considering one of the alleles, its allele frequency is the fraction of the number of occurrences of the allele, relative to the total number of all alleles at the same locus. Drift is the accumulation of chance factors that affect allele frequency: variations that result from random sampling.
That removes the mention of odd/even numbers. Johnuniq (talk) 00:28, 23 March 2009 (UTC)
replies: text: I know-we are all challenged getting the words right.  I like your idea of giving a "for instance", but it's better to remove this one since we know there are problems with it. Professor marginalia (talk) 22:20, 23 March 2009 (UTC)
thread_title: Explanation

message: Ettrig-can you clarify that the glossary definition of allele/gene frequency requires 2 or more allele variants in the population to qualify under the definition of allele frequency? It's quite possible to have an allele frequency of 1 or 100% (allelic homogeneity), isn't it? The case in which there is just one variant of the allele in the population?  Thanks. Professor marginalia (talk) 17:22, 28 March 2009 (UTC)
replies: text: Hmm... Futuyma says several. Not in allele frequency but in immediately preceding allele. I modified slightly to two or more. Are you challenging this or requesting that it is expressed more clearly? --Ettrig (talk) 17:43, 28 March 2009 (UTC)
replies: text: Maybe it's expressed unclearly, otherwise I don't understand this definition at all.  Can you quote it verbatim?  The definition seems to be requiring 2 or more allele variants, and I don't think that's a meaningful requirement.  Populations can and do have allele frequencies of 100% for certain alleles. There are not 2 or more variants in those cases.  Especially pronounced when we're talking about genetic drift in small populations, there is a random tendency toward homogeneity of alleles--and at this point the population no longer has a measured frequency for the alleles?  I can't envision any potential value in drawing a definitional line requiring there be two or more allele variants.Professor marginalia (talk) 18:06, 28 March 2009 (UTC)
replies: text: Definitions of allele: (1) One of several forms ... (2) An alternative form ... (3) (alleles)  alternative forms ... (4) One of the different homologous forms ... (5) Any of the alternative states ... The first one is Futuyma. If we go by definitions given, the pattern is clear. Alleles are supposed to occur in plural. But I don't think anyone would protest if an allele frequency reached 100%. Hartl & Clark says on p. 96 Eventually the population will have either all A alleles or all a alleles. Here they are talking about a situation with only one allele, as you expected. --Ettrig (talk) 18:39, 28 March 2009 (UTC)
replies: text: While you can certainly have an allele frequency of 1, that's sort of irrelevant in the context of drift - you can't have drift if a single allele has fixed, after all. Graft | talk 00:07, 29 March 2009 (UTC)
replies: text: You say (1) requiring 2 or more allele variants is not a meaningful requirement and (2) allele frequency of 1 is irrelevant. These two comments point in opposite directions. Maybe it would help you to observe that the quote from Hartl is about the transition from a situation with two alleles to a situation with "one". --Ettrig (talk) 06:19, 29 March 2009 (UTC)
replies: text: Okay, maybe it will be less confusing if I restate this.  An allele frequency can be 1 or 0.  Genetic drift for Allele A cannot occur if Allele A is 1 or 0. Both true.  Allele frequencies of 1 are relevant to genetic drift because in an isolated population, genetic drift has a tendency to eventually push an allele frequency to 1 (or 0).  Once it gets there, no drift possible.  Whole point being, let's not imply that the definition of "allele frequency" applies only to alleles in populations where there are multiple allele variants.  We can say genetic drift is actively occurring only when there are multiple allele variants.  But it's a mistake to say that's what the term "allele frequency" itself means. Professor marginalia (talk) 19:43, 29 March 2009 (UTC)
thread_title: Futuyma

message: In the bacteria example given, the population is allowed to breed for many generations and then the surviving organisms are examined to determine frequencies of A and B.  The probabilities for those frequencies are calculated.  But can we say the probabilities remain consistent for x, x+1,x+2...x+? generations? Is this accurate?  Given that the probabilities are memory-less between the begin point and the end over a span of multiple generations, and given that absorbing boundaries will usually cause alleles to disappear completely in the end, I can't see how these tendencies are consistent with unchanging probability (as given in biological example section) of a fixed allele, 1/16. Doesn't Markov say the probability of fixity in this case is the same as its freq distribution in the original population? Or 50%?Professor marginalia (talk) 22:40, 1 April 2009 (UTC)
replies: text: Yes, this is an unrealistic assumption made to provide a very simple model. The assumption is that all the bacteria divide at the same time and that none die in this period. This assumption is very similar to the one made in the Fisher-Wright model, that a very big and perfectly representative set of gametes is generated. --Ettrig (talk) 06:53, 2 April 2009 (UTC)
replies: text: What you're saying in this example is that all bacteria reproduce exactly equally, as do all their offspring, all of them surviving until - poof - they are all simultaneously killed, en masse, except 4?  There is really isn't any genetic drift to speak of occurring yet in this example then-we've described a catastrophe and the 1/16 odds all who survive it share the same allele.  This is a population bottleneck, but unless and until these 4 survivors (the random sample) breed, there is no real process underway showing drift from the sampling. Professor marginalia (talk) 22:40, 2 April 2009 (UTC)
thread_title: Pedantic question? biological example

message: The example about 100 bacteria gives incorrect probabilities. The odds of getting 4 A's is not 1/2*1/2*1/2*1/2=1/16, but rather 25/50*24/49*23/48*22/47=303600/5527200=253/4606
All the odds are
*4A's= 253/4606 
*3A's= 575/2303 
*2A's= 900/2303 
*1 A = 575/2303 
*0A's= 253/4606 
JedG (talk) 05:03, 26 May 2009 (UTC)
replies: text: Agreed, it is faulty. Given that one of the expected 50 As have been identified, the expected remainder is 49. My intention when introducing this example was to be able to show drift with as simple calculations as possible. In somewhat other words, a situation that is possible, that exemplifies drift and that can be analyzed with simple calculations. The first version did not mention the peak population size. Would it be OK to state that the population rises to enourmous amounts, then falls back to 4? --Ettrig (talk) 07:42, 26 May 2009 (UTC)
replies: text: Perhaps the best thing to do would just say that there is a very large group to begin with. The larger the group the less the difference will be from the values given. No need to state actual numbers at the beginning. I am fine with using simple examples, as they are best for teaching, just make sure that you don't make any inaccurate statements. JedG (talk) 09:03, 26 May 2009 (UTC)
replies: text: OK, I will make this change. Would appreciate if you keep keeping an eye on it. --Ettrig (talk) 10:27, 26 May 2009 (UTC)
replies: text: I'm not sure what this example is meant to demonstrate; there's a lot of probability computation, but it doesn't clarify what exactly "drift" is in all those machinations - less calculation, more explanation is required, I think. Graft | talk 18:05, 27 May 2009 (UTC)
thread_title:  Faulty Probability 

message: 1. How would the marbles-in-a-jar analogy arise in the wild?
:The real phenomenon that this is an analogy of is assumed to happen all the time. --Ettrig (talk) 18:44, 19 June 2009 (UTC)
replies: text: The sentence in itself is inconsistent. According to my memory the equation is correct in this respect, so I will remove inversely. --Ettrig (talk) 18:44, 19 June 2009 (UTC)

text: Drift toward frequency 0 has the same speed as drift toward 1. So if the starting frequency is exactly in the middle, the expected time to 0 is the same as the expected time to 1. --Ettrig (talk) 18:44, 19 June 2009 (UTC)

text: Trivial mistake. Expectation value is better concept in this context. Have changed. --Ettrig (talk) 19:10, 19 June 2009 (UTC)

text: I have made the same observation. Have seen the same kind of graph in several textbooks. None other with the same "problem". I would like to put other graphs here. But in earlier discussions a strong view voiced was that drift would drow in other effects for large population sizes. So I got stuck. --Ettrig (talk) 19:10, 19 June 2009 (UTC)

text: The effect is that many gene variant are lost, which is seen as small remaining amounts of gene variants. Yes, this is consistently observed. --Ettrig (talk) 19:10, 19 June 2009 (UTC)

text: The mutation is almost always a small minority (1/N). Therefore it has low probability of being fixed by drift and the time for this to happen, when it happens, is long. Yes, I think this is the normal view of drift and I see not problem with it. If there is one, I would be interested to know about it. --Ettrig (talk) 19:16, 19 June 2009 (UTC)

text: It is very difficult to determine for a specific frequency change to what extent it was caused by drift and to what by selection. We "never" know all the selective forces. --Ettrig (talk) 19:10, 19 June 2009 (UTC)

text: I am also unhappy with this sentence. Probability theory does not say anything about genetic drift. Those conclusions have to be inferred or deduced. I think what is hinted at is that the sampling error (=genetic drift) is smaller for larger populations. This is important for each allele. Whether this leads to convergence depends on the combined effects of Genetic Drift, Mutation, Selection and what else. For a larger population, the same selective pressure is more likely to determine whether a particular allele will be fixed or not. --Ettrig (talk) 09:47, 19 January 2012 (UTC)
replies: text: Fixed the sentence.Joannamasel (talk) 17:46, 21 January 2012 (UTC)
thread_title:  Questions 

message: The history section could use full references to the works that are mentioned ("Sewall Wright ... 1929", "the work of Ernst Meyer" etc) in addition to the secondary sources. Narayanese (talk) 21:21, 3 November 2009 (UTC)
thread_title:  Primary sources 

message: The description of the jar experiment does not make clear that at each step, the marble has to be returned to the original jar before selecting the next one. When I first read it, I puzzled over the process, and just couldn't understand how it could work... until I realized that the this was what was intended and it just was not stated explicitly when describing the experiment. I've added a sentence to make it clear. (If by chance I've misunderstood, please fix it.) Omc (talk) 07:48, 3 February 2010 (UTC)
replies: text: I remember puzzling over the same problem. My "solution" was to notice that the text does not say that the selected marble is removed from the jar. I tried to clarify this. I do not want the text to say that the marble is removed. That would make it more complex, in my view. --Ettrig (talk) 07:47, 4 February 2010 (UTC)
replies: text: To me it's more natural to describe the process as "remove one marble from the jar, examine it, and return it". Any experiment like this is typically described by saying "remove one marble from the jar", I think. The image of selecting one marble but leaving it in the jar (pushing your fingers deep into the jar at each step to select a random marble?) seems awkward. But this is quibbling - my main point is that we needed to make it clear that at each step we're selecting one marble from the whole population (20), rather than removing a marble and setting it aside and then selecting from the remaining marbles (19, 18, 17, ...). Your version also makes that clear, and it's fine. Omc (talk) 17:41, 4 February 2010 (UTC)

text: The jar model could be explained more clearly. It could include sentences like these: "Because each marble is returned to the jar, the percentage that are blue does not change during the initial sampling round (which chooses marbles randomly). Therefore, each time a marble is chosen, it is equally likely to be blue or red. Replacement of the "parent" marble in the first jar is necessary to keep the probabilities constant. It's therefore possible (indeed, likely) that by chance more blues will be chosen than red (or the converse), just as N successive coin tosses can lead to sequences with more heads than tails (or the converse). In both cases the initial outcomes are given by the binomial distribution with p = 0.5. In the Figure, the number of times particular marbles are selected are indicated by the number of dots within the marbles. Some marbles are not chosen, others are chosen 1 or more times (in the first set of 20 samples illustrated, one marble happens to be chosen 5 times). However, when the sampling process is repeated, to create the third jar, the probabilities of drawing blue and red marbles changes (p > or < 0.5 for the binomial distribution) because there may be more (or less) blue marbles in the second jar as a chance result of the first round of random sampling. In the case illustrated, there was a majority of blue marbles in the second jar, so the new samplings needed to create the third jar are now biassed in favor of blue selections. This can eventually (and in the case illustrated, after only 5 rounds) lead to an entirely blue jar. Additional sampling rounds will no longer change the outcome, which is "fixated"."
This is rather long-winded and not necessary for those who already understand what is going on - but those people don't read Wikipedia! Paulhummerman (talk) 03:48, 14 November 2017 (UTC)
replies: text: Yes, surely some of this could be added. If you are unsure, make the change in small steps and allow some time for reactions in between. Please avoid saying the same thing twice or more, such as the percentage that are blue does not change, equally likely, probabilities constant. --Ettrig (talk) 11:47, 14 November 2017 (UTC)
thread_title:  Unexplained step in jar experiment 

message: Can someone provide information about Moran from "Moran model"? Maybe a link to a page (stub) with that name?
Is Moran model identical with or related to Moran process?
132.66.40.82 (talk) 16:07, 28 October 2010 (UTC)
replies: text: Yes it is identical to the Moran process, I added the link, and that page in links to Pat Moran who developed it.Joannamasel (talk) 17:52, 28 October 2010 (UTC)
thread_title:  Who is Moran? 

message: The following statement has been marked with "citation needed" and as "dubious - disputed" in the main article:“In contrast to natural selection, which makes gene variants more common or less common depending on their reproductive success, [2] the changes due to genetic drift are not driven by environmental or adaptive pressures, and may be beneficial, neutral, or detrimental to reproductive success.”The reason is the following: if the changes due to genetic drift were other than neutral (viz. beneficial or detrimental to reproductive success) then they would be made "more common or less common depending on their reproductive success". Therefore they would be indistinguishable from random mutations upon which natural selection operates.
The warnings should not be removed until the present dispute is resolved.Miguel de Servet (talk) 10:41, 17 January 2011 (UTC)
replies: text: The statement should be clarified something like this: Since the effect of genetic drift is random, it may make a detrimental allele more common as likely as less common and vice versa a beneficial allele less common as well as more common. For alleles that are not neutral, the total change is the effect of selection plus the effect of drift. Hope this helps. --Ettrig (talk) 11:20, 17 January 2011 (UTC)
replies: text: "if the changes due to genetic drift were other than neutral (viz. beneficial or detrimental to reproductive success) then they would be made "more common or less common depending on their reproductive success"--not necessarily.  For example, in very small populations the magnitude of the drift can be greater--outpacing the lesser effect the allele has on reproductive success.  Take the evolution of alleles in a population which are detrimental only in individuals who are homozygous for it--such as Tay-Sachs disease which is fatal before the individual reaches reproductive age.  Drift and natural selection may both operate on the allele, but if drift overshadows the selection then the evolution, the change in frequency of the trait, results from drift. I don't quite understand the latter point about mutations.  Random mutation is a source of new alleles in a population.  Natural selection and random drift are two very different mechanisms that increase or decrease the frequency distribution for the mutation in a population.Professor marginalia (talk) 17:07, 17 January 2011 (UTC)
thread_title:  Can changes due to genetic drift be beneficial or detrimental to reproductive success?   

message: Both Hartl & Clark and Hartwell et al state the H&W conditions first, including random mating, then state that frequencies remain constant under these conditions. If we are to remove the random mating condition, which seems reasonable, we need to refer to another source. --Ettrig (talk) 19:02, 12 February 2011 (UTC)
replies: text: The usual 5 HW assumptions lead collectively to two HW results, ie constant allele frequency, and genotype frequencies of p^2, 2pq and q^2. But taking only one of the two results, not all 5 assumptions are needed. There is an excellent and authoratitive discussion of HW in Ewens' "Mathematical Population Genetics", although this source is perhaps a bit inaccessible to a casual reader. I am not sure which other books cover this subject carefully enough. Shall we cite Ewens?Joannamasel (talk) 22:25, 12 February 2011 (UTC)
replies: text: Yes, certainly. There is no requirement that the cited source is accessible on the web. I found this but didn't have the patience to determine whether it supports the reduction of assumptions. If it can be used, please specify one or a few pages. --Ettrig (talk) 06:53, 13 February 2011 (UTC)
thread_title: Random mating

message: Hello Genetic Drift Editors. I thought i would add the Sewall Wright picture to the article because 1) he was a major contributor in our understanding of the topic and 2) I thought that after alot of the charts that are in the article thought it would be nice to add a face in their to kind of associate with article. This such a well done article I just wanted to give it an extra kick.--Jraffe0404 (talk) 04:54, 6 March 2011 (UTC)
thread_title:  Picture 

message: I'm not very fond of the paint analogy. I'll think about it and perhaps try to be more constructive.
212.126.224.100 (talk) 13:57, 23 August 2011 (UTC)
replies: text: You might be interested in looking at the version that was here before user:Graft rewrote it completely, December 23 2010. --Ettrig (talk) 14:50, 23 August 2011 (UTC)

text: The "cans of paint" analogy makes no sense because there is no "copying" or "replication" of the paint in the process.  Genes aren't a handoff, a give and get, between parent and offspring (in the example paint is being poured from one pail to another, with the original remaining full as if by magic).  It's a weird and confusing image, imo, this oddly behaving farmer and his magic paint cans. Professor marginalia (talk) 19:09, 27 January 2012 (UTC)
replies: text: I changed it back to the GA version. I'm not sure that the analogy section (in either form) fits the rest of the article well, but at the very least if we are going to have one the alleles need to be copied, not handed-off like the baton in a relay, from one generation to the next.  And at least marbles are discrete units, like alleles. Symbolizing them as "ever-filling paint cans" is a bit more confusing. Professor marginalia (talk) 19:34, 15 May 2012 (UTC)
thread_title:  Paint 

message: I find the text about other models very difficult to understand. 
If the variance in the number of offspring is much greater than that given by the binomial distribution assumed by the Wright-Fisher model, then given the same overall speed of genetic drift (the variance effective population size), genetic drift is a less powerful force compared to selection.[9] If higher moments of the offspring number distribution exceed those of the binomial distribution then again the force of genetic drift is substantially weakened.[10]
Should the variance effective population size be changed to the variance in the effective population size? This form normally means that the variance is an alternative to overall speed. But they are not of the same kind. Should we also add ... is the same? I am also completely lost on moments of the offspring number distribution. --Ettrig (talk) 10:18, 27 January 2012 (UTC)
replies: text: "Variance effective population size" is a technical term, and I edited the link to go directly to that. Ditto for moments of a distribution. I agree that the text is difficult, but genetic drift really is an technical mathematical subject, even if that's not how it is taught in intro classes. Joannamasel (talk) 16:44, 27 January 2012 (UTC)
thread_title:  Other models 

message: Could someone please remove (or thoroughly rewrite) this. It is completely out of style with the rest of the article. (I am out of reverts.) --Ettrig (talk) 16:53, 24 November 2015 (UTC)
thread_title:  Out of style passage near end of history 

message: "which claims that most instances where a genetic change spreads across a population (although not necessarily changes in phenotypes) are caused by genetic drift acting on neutral mutations.[6][7]"
I found the relationships between the three concepts, "phenotype," "genetic drift," and "genetic change" impossible to unravel! I understand the concepts themselves, I just don't understand what this sentence is trying to say about them.  
OmneBonum (talk) 07:25, 21 February 2019 (UTC)
replies: text: most instances where an allele becomes the most common variant in a population it is not because it is selected for, but because of random changes in allele frequencies. Most of the allele changes that become common this random way have no or negligible effect on the phenotype. --Ettrig (talk) 08:11, 21 February 2019 (UTC)
thread_title:  Unclear wording 

message: — Assignment last updated by RuthBenander (talk) 14:05, 28 September 2023 (UTC)
thread_title: Wiki Education assignment: First Year English Composition 1001

message: “To represent this reproduction, randomly select BUT DO NOT REMOVE a marble from the original jar and deposit a new marble with the same colour into a new jar.”
I struggled a little with the logic of this analogy until I understood it as amended above. If I select a kitten from a litter I take it with me. 
Someone with more authority could make the change if deemed helpful. =avallone (talk) 15:02, 5 May 2024 (UTC)
thread_title:  Marble analogy