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A summary of this article appears in evolution. |
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)
This article was the subject of a Wiki Education Foundation-supported course assignment, between 31 August 2020 and 18 December 2020. Further details are available
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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)
I have disliked the use of random sampling here for a long time on pedagogical grounds. Now found a factual argument that I wasn't aware of and don't quite understand. The process of change in allele frequency due solely to chance effects is called random genetic drift. One should note, however, that random genetic drift can also be caused by processes other than the sampling of gametes. For example, stochastic changes in selection intensity can also bring about random changes in allele frequencies. Li & Graur, Fundamentals of Molecular Evolution, 1991, page 28. -- Ettrig ( talk) 20:31, 19 February 2009 (UTC)
I've removed the link to the statistics page. Statistics concerns a method of measurement: "The mathematics of the collection, organization, and interpretation of numerical data", so, unless genes "collect, organize, and interpret numerical data" and this activity then motivates them to act in a certain manner, whatever is being attempted to be explained in the introduction here it seems clear that it is not the statistical technique the link points to. I would like to add here that imo the introduction needs to be rewritten. It oscillates between jargon and kindergarten levels of prose and seems to me to be both clumsy and opaque, even if, in some sense, it might be considered accurate. It is also repetitive. LookingGlass ( talk) 07:18, 6 March 2014 (UTC)
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)
I like keeping "four processes" as a link to Population genetics (thanks for the link). I take the point that "small changes", "slow changes", "long run" are rather weasely, and I can't offer an authoritative opinion re alternative wording. Do you know of any clear, sourced statements that shed light on this? It seems obvious that in anything more than a population of 100 individuals, inter-generational changes due to drift will be "small", but I take the point that by evolutionary standards, an allele could be lost from a small population quite quickly due to drift. I haven't seen much clear discussion on the relative significance of the four processes, and I wouldn't support switching from saying that drift gives small/slow changes, to the opposite of making the unqualified statement that it can account for a large proportion of changes, without a source. It seems very plausible that some species would have been strongly influenced by drift, or even that nearly all species have been significantly influenced. But I think we need an accepted source before possibly giving readers the idea that a large proportion of evolution is due to genetic drift (was a large proportion of the evolution of the eye due to drift?). -- Johnuniq ( talk) 00:57, 25 February 2009 (UTC)
as a casual reader just looking for a quick understanding of the concept of genetic drift, i hit a brick wall before i even finished the first sentence, i got the hell out of here before wasting another minute and found a perfect little page via Google, that explained it to me, quick and dirty, with only a 10 second investment in time; often, Wikipedia articles these days seem so incredibly opaque and poorly written: simple and clear sentences are rejected in favor of complex and ambiguous ones; well, there's my two cents, don't go spending it all in one place, cheers — Preceding unsigned comment added by 69.250.176.112 ( talk) 23:27, 30 June 2011 (UTC)
I fully agree with the above of 30 June, 2011. The lede does not meet Wiki's standards. One of the obvious problems is the use of required hypertexting without a clue of it's meaning within the sentence (lazy hypertexting). Certainly one should not be required to begin the treacherous and potentially endless journey to other articles also dependent on lazy hypertexting, those themselves also dependent on lazy hypertexting... — within the opening paragraph! (There lies a systemic Wikipedia fault.) See also:
Wikipedia:Manual of Style (lead section), in particular: "The lead section should briefly summarize the most important points covered in an article in such a way that it can stand on its own as a concise version of the article," and "In general, specialized terminology and symbols should be avoided in an introduction."
Notice how the definition is handed off to hypertexed jargon, thus is NEVER defined here: Quoting first paragraph:
"Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.[1] The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. A population's allele frequency is the fraction of the copies of one gene that share a particular form.[2] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation."
...And are we really to believe that Genetic drift is caused by random sampling? And so forth. We seemingly need fewer experts and more teachers/communicators here.
--
69.110.91.50 (
talk)
22:37, 18 December 2011 (UTC)Doug Bashford
relative frequency is probably just a halfway transition from relative abundance to frequency. That is trivial. But my real complaint is about the use of frequency in the first sentence. Allele frequency is explained in that article. But not even frequency (disambiguation) has the meaning used in this context. The closest thing is number of times of occurrence in an experiment. So we cannot expect frequency to be correctly understood by a large majority of the readers. Maybe relative abundance is too cumbersome. But frequency just will not do. -- Ettrig ( talk) 16:15, 5 March 2009 (UTC)
ref num | Websters | Penguin | Oxford | Wiktionary |
1979 | 1969 | 1963 | Current | |
1 | (originally) condition of being crowded, a crowd | |||
2 | the fact of occurring often or repeatedly, frequent occurrence | continual repetition | frequent occurrence | the property of occurring often rather than infrequently |
3 | the number of times any action or occurrence is repeated in a given period | number of repetitions (in a given time) | the rate of occurrence of anything; the relationship between incidence and time period | |
4 | in mathematics and statistics, (a) the ratio of the number of actual occurrences to the number of possible occurrences in a given period; (b) the ratio of the number of individuals occurring in a specific class to the total number of individuals under survey | (statistics) the number of observations having a value between two specified limits | ||
5 | in physics, (a) the number of vibrations or cycles per unit of time; (b) the number of cycles per second of an alternating electric current | number of vibrations (of wave) per second | number of repetitions (in a given time) | the quotient of the number of times n a periodic phenomenon occurs over the time t in which it occurs: f = n / t |
The table above shows some dictionary definitions. The sense used in this article is Webster 4 (b). This sense is a technical term used in mathematics and statistics. It is not even given as a biology concept. The fact that it is used is natural, given the close relation between population genetics and statistics and probability. This sense is missing in the other dictionaries, possibly very peculiarly expressed in Penguin. Note also how all the other senses (disregarding obsolete number 1) are related to time, which the use in this article is not. The conclusion is clearly that frequency with this meaning cannot be used without explanation in the first sentence in a Wikipedia article. -- Ettrig ( talk) 18:51, 8 March 2009 (UTC)
We should absolutely say frequency in the first sentence. "Allele frequency" is an indispensable term when talking about drift, and the sooner the reader is introduced to this usage, the better. What's wrong with the current formulation? It seems relatively unambiguous about what "frequency" means here - what fraction of the population has a particular allele. Is the reader going to get confused and think we're talking about cycles or something? We're not supposed to assume the reader is an idiot, here. Graft | talk 23:51, 16 March 2009 (UTC)
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)
It's hard to get the words right. What about replacing the whole paragraph with:
That removes the mention of odd/even numbers. Johnuniq ( talk) 00:28, 23 March 2009 (UTC)
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)
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)
The current text on founder effect confuses founder effect with bottleneck. Founder effect occurs only at the moment of founding, when the founders are sampled from the population of origin. The current text erroneously also includes the drift that occurs after the founding. Stearns and Hoekstra, p 65, describes founder effect with New populations are sometimes founded by a small group of individuals in which gene frequencies differ considerably from the frequencies in the parent population. Glossary of Futuyma The principle that the founders of a new colony carry only a fraction of the total genetic variation in the source population. Glossary of Strickberger ... Since these founders carry only a small fraction of the parental population's genetic variability, radically different gene frequencies can become established in the new colony. I left some text that contradicts this, because it was supported with sources that I cannot check. Please, could somebody else check those? -- Ettrig ( talk) 19:43, 13 May 2009 (UTC)
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
JedG ( talk) 05:03, 26 May 2009 (UTC)
1. How would the marbles-in-a-jar analogy arise in the wild?
2. Under "Time to fixation or loss", second paragraph says Time to Fixation is inversely proportional to population size. Tfixed equation says it's directly proportional. Which is correct?
3. The values for Tfixed and Tlost are the same when p = 0.5. How is this to be interpreted?
4. What is "mean average" in the para. under the Tfixed eqn? In statistics, mean and average are identical.
5. The simulation results shown on the right are incomplete. According to the Tfixed eqn, the first should go beyond 55 generations to show fixation, the second should go beyond 550, and the third should go beyond 5500.
6. The progression in simulation results for the three population sizes suggests that genetic drift would not occur at all in large populations. Implications should be discussed in the text.
7. The simulation results suggest that the genetics of a small, isolated population of Mountain Goats, say, should wander all over the place from one generation to the next. Has this been observed in the wild?
8. The very last equation in the subsection gives values that are much greater than 1.0 (e.g., 10.8 for N = 20), indicating that mutations take much longer to be fixed and are therefore more likely to be lost. Is this consistent with other theories in genetics?
9. The article is purely theoretical. Have examples of genetic drift been observed in the wild? Some sort of observational verification should be cited. Virgil H. Soule ( talk) 18:03, 19 June 2009 (UTC)
10. "In probability theory, the law of large numbers predicts little change taking place over time when the population is large. " Is this statement accurate? Surely the relevance of the LLN is that fitnesses would converge on expected values, reducing the buffeting of drift on non-neutral alleles. If the neutral fixation rate is the mutation rate, then don't all populations change at the same rate (for neutral alleles)? I thought that was the point of the molecular clock? Allangmiller ( talk) 00:58, 18 January 2012 (UTC)
Reviewer: Sasata ( talk) 05:36, 29 October 2009 (UTC) Hi, I'll be doing this review. I'm going to try and dig up my old class notes on the topic to refresh myself with the subject material before digging into the article. In the meantime, could the editor(s) please ensure that every major paragraph has a citation? It will be required for GA promotion. Hope to be finished a set of initial comments in about 4-5 days. Sasata ( talk) 05:36, 29 October 2009 (UTC)
Ok, I've just read the article closely and made some minor copyedits to the text. I must say I'm impressed with the readability of the article, and I think it serves as an excellent introduction to the topic. Just two things I'd like to see:
Hi again, how are we doing with this review? I see some progress has been made in getting the article citation-compliant, but there's still many unreferenced paragraphs. Is more time required? Do you want some assistance? Sasata ( talk) 15:36, 10 November 2009 (UTC)
Ok, it looks good now. Thanks to you (and Narayanese) for helping to make a good article which will benefit countless students of genetics! Sasata ( talk) 23:46, 28 November 2009 (UTC)
What relevance does homologous recombination have to genetic drift? Emw ( talk) 04:15, 30 October 2009 (UTC)
(unindent) I just came across two papers relevant to the discussion:
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link)At the moment I don't have time to adequately summarize those papers here, but thought I would note that they seem useful here because they discuss the relationship between genetic drift and recombination in the evolution of pathogens (with data from P. falciparum). Emw ( talk) 05:02, 14 November 2009 (UTC)
At the very top of this talk page (19 February 2009, maybe time to archive) I questioned the limitation of the genetic drift concept to sampling error. My view is that genetic drift should include all stochasticity in alele frequency changes. But there was considerable opposition, supported with authoritative sources, so I gave up. But now I am happy to see that the latest major addition widens the concept. But I am unhappy with details in the formulations. The most important one (imho) is that variability is misssing.
Please note the word variance in Desgraves. The hitchiking pulls in different directions at different times because of recombination. This adds stochasticity in the reproductive success. Such stochasticity is part of the more general definition of genetic drift. In the evolutionary time scale, recombination happens very often, so the effect is almost exclusively random. It seems to me that the variation aspect is not present in the present article. -- Ettrig ( talk) 15:33, 15 November 2009 (UTC)
I read parts of the referenced article by Sella et al. It clearly states in the abstract that the view presented is controversial and tentative. Such material should not be presented as the view of Wikipedia. I look forward to a very interesting discussion about this. -- Ettrig ( talk) 12:38, 18 November 2009 (UTC)
The following excerpt is problematic: Selection causes the effect size of genetic drift to vary across the genome. The effective population size is reduced by selection (by a factor f0 which is the equilibrium frequency of alleles that are not eliminated by selection), increasing the genetic drift at the locus. Also nearby loci are affected as a result of genetic linkage. The statement in the last sentence should be first. The linkage is part of the explanation of the reduction of effective population size. (By linkage, deleterious mutations remove subsets of gametes, leaving only f0*Ne for our mutations to spread in.) It is not reasonable to expect the Wikipedia reader to understand what equilibrium frequency refers to here. My interpretation is that it refers to the frequency of non-mutated gametes that is maintained by selection when a stream of deleterious mutations remove the other gametes. -- Ettrig ( talk) 21:58, 28 November 2009 (UTC)
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)
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)
Hmmm. This illustration/experiment seems overcomplicated. The process being decribed would seem essentially to be:
There are two colours of marbles in a group. 1. Choose one of these colours > Record your choice > Repeat x20. 2. Compare the proportions of colours in your record and the original.
From the article it seems that no more is being said than that the proportion of alleles in a future generation is determined by random selection as well as by natural selection. If this is the case, then rather than dive straight into abstruse mathematical expression, some real examples of this mechanism of chance (picking of the colour of marble for the new group) would help make the point better. LookingGlass ( talk) 08:02, 6 March 2014 (UTC)
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)
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)
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)
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)
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)
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)
This sentence The effect of genetic drift is larger for alleles present in a smaller number of copies, and smaller when an allele is present in many copies. is criticised. Copies of what? The answer is copies of alleles. When the question is posed, I think this could be interpreted as alleles in copies of something. We want to say When there are few copies of an allele, the effect of genetic drift is larger, and the effect is smaller when there are many copies. I came here to ask for help with the formulation. But I will try this and hope it provokes improvement. -- Ettrig ( talk) 06:23, 19 December 2011 (UTC)
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)
I've proposed a change to the lead sentence of the natural selection page, and I think a corresponding change should be made to the lead sentence of this page.
My proposed lead sentence for natural selection is "Natural selection is the differential survival and reproduction of individuals due to differences in phenotype."
My proposed lead sentence for this page is "Genetic drift is the differential survival and reproduction of individuals due to chance". (the reference can stay)
These edits would make the descriptions more accurate, and help highlight the parallels (and by doing so also the fundamental differences) between natural selection and genetic drift.
I can see that some sort of joiner sentence would need to follow; perhaps "From a genetic perspective, it can be defined as change in allele frequencies in a population due to chance." 129.127.101.245 ( talk) 06:05, 25 September 2015 (UTC)
I agree with Joanna on this - I wouldn't want to try to redefine the historical and accepted definition of genetic drift on this page. ( Aaronragsdale ( talk) 17:47, 29 September 2015 (UTC))
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)
"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)
This article was the subject of a Wiki Education Foundation-supported course assignment, between 23 August 2023 and 30 November 2023. Further details are available
on the course page. Student editor(s):
Amaner222 (
article contribs).
— Assignment last updated by RuthBenander ( talk) 14:05, 28 September 2023 (UTC)
“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)
![]() | Genetic drift has been listed as one of the Natural sciences good articles under the good article criteria. If you can improve it further, please do so. If it no longer meets these criteria, you can reassess it. | |||||||||
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![]() | This ![]() It is of interest to the following WikiProjects: | |||||||||||||||||||||||
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A summary of this article appears in evolution. |
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)
This article was the subject of a Wiki Education Foundation-supported course assignment, between 31 August 2020 and 18 December 2020. Further details are available
on the course page. Student editor(s):
Krsmith09.
Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT ( talk) 22:11, 16 January 2022 (UTC)
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)
I have disliked the use of random sampling here for a long time on pedagogical grounds. Now found a factual argument that I wasn't aware of and don't quite understand. The process of change in allele frequency due solely to chance effects is called random genetic drift. One should note, however, that random genetic drift can also be caused by processes other than the sampling of gametes. For example, stochastic changes in selection intensity can also bring about random changes in allele frequencies. Li & Graur, Fundamentals of Molecular Evolution, 1991, page 28. -- Ettrig ( talk) 20:31, 19 February 2009 (UTC)
I've removed the link to the statistics page. Statistics concerns a method of measurement: "The mathematics of the collection, organization, and interpretation of numerical data", so, unless genes "collect, organize, and interpret numerical data" and this activity then motivates them to act in a certain manner, whatever is being attempted to be explained in the introduction here it seems clear that it is not the statistical technique the link points to. I would like to add here that imo the introduction needs to be rewritten. It oscillates between jargon and kindergarten levels of prose and seems to me to be both clumsy and opaque, even if, in some sense, it might be considered accurate. It is also repetitive. LookingGlass ( talk) 07:18, 6 March 2014 (UTC)
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)
I like keeping "four processes" as a link to Population genetics (thanks for the link). I take the point that "small changes", "slow changes", "long run" are rather weasely, and I can't offer an authoritative opinion re alternative wording. Do you know of any clear, sourced statements that shed light on this? It seems obvious that in anything more than a population of 100 individuals, inter-generational changes due to drift will be "small", but I take the point that by evolutionary standards, an allele could be lost from a small population quite quickly due to drift. I haven't seen much clear discussion on the relative significance of the four processes, and I wouldn't support switching from saying that drift gives small/slow changes, to the opposite of making the unqualified statement that it can account for a large proportion of changes, without a source. It seems very plausible that some species would have been strongly influenced by drift, or even that nearly all species have been significantly influenced. But I think we need an accepted source before possibly giving readers the idea that a large proportion of evolution is due to genetic drift (was a large proportion of the evolution of the eye due to drift?). -- Johnuniq ( talk) 00:57, 25 February 2009 (UTC)
as a casual reader just looking for a quick understanding of the concept of genetic drift, i hit a brick wall before i even finished the first sentence, i got the hell out of here before wasting another minute and found a perfect little page via Google, that explained it to me, quick and dirty, with only a 10 second investment in time; often, Wikipedia articles these days seem so incredibly opaque and poorly written: simple and clear sentences are rejected in favor of complex and ambiguous ones; well, there's my two cents, don't go spending it all in one place, cheers — Preceding unsigned comment added by 69.250.176.112 ( talk) 23:27, 30 June 2011 (UTC)
I fully agree with the above of 30 June, 2011. The lede does not meet Wiki's standards. One of the obvious problems is the use of required hypertexting without a clue of it's meaning within the sentence (lazy hypertexting). Certainly one should not be required to begin the treacherous and potentially endless journey to other articles also dependent on lazy hypertexting, those themselves also dependent on lazy hypertexting... — within the opening paragraph! (There lies a systemic Wikipedia fault.) See also:
Wikipedia:Manual of Style (lead section), in particular: "The lead section should briefly summarize the most important points covered in an article in such a way that it can stand on its own as a concise version of the article," and "In general, specialized terminology and symbols should be avoided in an introduction."
Notice how the definition is handed off to hypertexed jargon, thus is NEVER defined here: Quoting first paragraph:
"Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.[1] The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. A population's allele frequency is the fraction of the copies of one gene that share a particular form.[2] Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation."
...And are we really to believe that Genetic drift is caused by random sampling? And so forth. We seemingly need fewer experts and more teachers/communicators here.
--
69.110.91.50 (
talk)
22:37, 18 December 2011 (UTC)Doug Bashford
relative frequency is probably just a halfway transition from relative abundance to frequency. That is trivial. But my real complaint is about the use of frequency in the first sentence. Allele frequency is explained in that article. But not even frequency (disambiguation) has the meaning used in this context. The closest thing is number of times of occurrence in an experiment. So we cannot expect frequency to be correctly understood by a large majority of the readers. Maybe relative abundance is too cumbersome. But frequency just will not do. -- Ettrig ( talk) 16:15, 5 March 2009 (UTC)
ref num | Websters | Penguin | Oxford | Wiktionary |
1979 | 1969 | 1963 | Current | |
1 | (originally) condition of being crowded, a crowd | |||
2 | the fact of occurring often or repeatedly, frequent occurrence | continual repetition | frequent occurrence | the property of occurring often rather than infrequently |
3 | the number of times any action or occurrence is repeated in a given period | number of repetitions (in a given time) | the rate of occurrence of anything; the relationship between incidence and time period | |
4 | in mathematics and statistics, (a) the ratio of the number of actual occurrences to the number of possible occurrences in a given period; (b) the ratio of the number of individuals occurring in a specific class to the total number of individuals under survey | (statistics) the number of observations having a value between two specified limits | ||
5 | in physics, (a) the number of vibrations or cycles per unit of time; (b) the number of cycles per second of an alternating electric current | number of vibrations (of wave) per second | number of repetitions (in a given time) | the quotient of the number of times n a periodic phenomenon occurs over the time t in which it occurs: f = n / t |
The table above shows some dictionary definitions. The sense used in this article is Webster 4 (b). This sense is a technical term used in mathematics and statistics. It is not even given as a biology concept. The fact that it is used is natural, given the close relation between population genetics and statistics and probability. This sense is missing in the other dictionaries, possibly very peculiarly expressed in Penguin. Note also how all the other senses (disregarding obsolete number 1) are related to time, which the use in this article is not. The conclusion is clearly that frequency with this meaning cannot be used without explanation in the first sentence in a Wikipedia article. -- Ettrig ( talk) 18:51, 8 March 2009 (UTC)
We should absolutely say frequency in the first sentence. "Allele frequency" is an indispensable term when talking about drift, and the sooner the reader is introduced to this usage, the better. What's wrong with the current formulation? It seems relatively unambiguous about what "frequency" means here - what fraction of the population has a particular allele. Is the reader going to get confused and think we're talking about cycles or something? We're not supposed to assume the reader is an idiot, here. Graft | talk 23:51, 16 March 2009 (UTC)
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)
It's hard to get the words right. What about replacing the whole paragraph with:
That removes the mention of odd/even numbers. Johnuniq ( talk) 00:28, 23 March 2009 (UTC)
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)
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)
The current text on founder effect confuses founder effect with bottleneck. Founder effect occurs only at the moment of founding, when the founders are sampled from the population of origin. The current text erroneously also includes the drift that occurs after the founding. Stearns and Hoekstra, p 65, describes founder effect with New populations are sometimes founded by a small group of individuals in which gene frequencies differ considerably from the frequencies in the parent population. Glossary of Futuyma The principle that the founders of a new colony carry only a fraction of the total genetic variation in the source population. Glossary of Strickberger ... Since these founders carry only a small fraction of the parental population's genetic variability, radically different gene frequencies can become established in the new colony. I left some text that contradicts this, because it was supported with sources that I cannot check. Please, could somebody else check those? -- Ettrig ( talk) 19:43, 13 May 2009 (UTC)
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
JedG ( talk) 05:03, 26 May 2009 (UTC)
1. How would the marbles-in-a-jar analogy arise in the wild?
2. Under "Time to fixation or loss", second paragraph says Time to Fixation is inversely proportional to population size. Tfixed equation says it's directly proportional. Which is correct?
3. The values for Tfixed and Tlost are the same when p = 0.5. How is this to be interpreted?
4. What is "mean average" in the para. under the Tfixed eqn? In statistics, mean and average are identical.
5. The simulation results shown on the right are incomplete. According to the Tfixed eqn, the first should go beyond 55 generations to show fixation, the second should go beyond 550, and the third should go beyond 5500.
6. The progression in simulation results for the three population sizes suggests that genetic drift would not occur at all in large populations. Implications should be discussed in the text.
7. The simulation results suggest that the genetics of a small, isolated population of Mountain Goats, say, should wander all over the place from one generation to the next. Has this been observed in the wild?
8. The very last equation in the subsection gives values that are much greater than 1.0 (e.g., 10.8 for N = 20), indicating that mutations take much longer to be fixed and are therefore more likely to be lost. Is this consistent with other theories in genetics?
9. The article is purely theoretical. Have examples of genetic drift been observed in the wild? Some sort of observational verification should be cited. Virgil H. Soule ( talk) 18:03, 19 June 2009 (UTC)
10. "In probability theory, the law of large numbers predicts little change taking place over time when the population is large. " Is this statement accurate? Surely the relevance of the LLN is that fitnesses would converge on expected values, reducing the buffeting of drift on non-neutral alleles. If the neutral fixation rate is the mutation rate, then don't all populations change at the same rate (for neutral alleles)? I thought that was the point of the molecular clock? Allangmiller ( talk) 00:58, 18 January 2012 (UTC)
Reviewer: Sasata ( talk) 05:36, 29 October 2009 (UTC) Hi, I'll be doing this review. I'm going to try and dig up my old class notes on the topic to refresh myself with the subject material before digging into the article. In the meantime, could the editor(s) please ensure that every major paragraph has a citation? It will be required for GA promotion. Hope to be finished a set of initial comments in about 4-5 days. Sasata ( talk) 05:36, 29 October 2009 (UTC)
Ok, I've just read the article closely and made some minor copyedits to the text. I must say I'm impressed with the readability of the article, and I think it serves as an excellent introduction to the topic. Just two things I'd like to see:
Hi again, how are we doing with this review? I see some progress has been made in getting the article citation-compliant, but there's still many unreferenced paragraphs. Is more time required? Do you want some assistance? Sasata ( talk) 15:36, 10 November 2009 (UTC)
Ok, it looks good now. Thanks to you (and Narayanese) for helping to make a good article which will benefit countless students of genetics! Sasata ( talk) 23:46, 28 November 2009 (UTC)
What relevance does homologous recombination have to genetic drift? Emw ( talk) 04:15, 30 October 2009 (UTC)
(unindent) I just came across two papers relevant to the discussion:
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link)At the moment I don't have time to adequately summarize those papers here, but thought I would note that they seem useful here because they discuss the relationship between genetic drift and recombination in the evolution of pathogens (with data from P. falciparum). Emw ( talk) 05:02, 14 November 2009 (UTC)
At the very top of this talk page (19 February 2009, maybe time to archive) I questioned the limitation of the genetic drift concept to sampling error. My view is that genetic drift should include all stochasticity in alele frequency changes. But there was considerable opposition, supported with authoritative sources, so I gave up. But now I am happy to see that the latest major addition widens the concept. But I am unhappy with details in the formulations. The most important one (imho) is that variability is misssing.
Please note the word variance in Desgraves. The hitchiking pulls in different directions at different times because of recombination. This adds stochasticity in the reproductive success. Such stochasticity is part of the more general definition of genetic drift. In the evolutionary time scale, recombination happens very often, so the effect is almost exclusively random. It seems to me that the variation aspect is not present in the present article. -- Ettrig ( talk) 15:33, 15 November 2009 (UTC)
I read parts of the referenced article by Sella et al. It clearly states in the abstract that the view presented is controversial and tentative. Such material should not be presented as the view of Wikipedia. I look forward to a very interesting discussion about this. -- Ettrig ( talk) 12:38, 18 November 2009 (UTC)
The following excerpt is problematic: Selection causes the effect size of genetic drift to vary across the genome. The effective population size is reduced by selection (by a factor f0 which is the equilibrium frequency of alleles that are not eliminated by selection), increasing the genetic drift at the locus. Also nearby loci are affected as a result of genetic linkage. The statement in the last sentence should be first. The linkage is part of the explanation of the reduction of effective population size. (By linkage, deleterious mutations remove subsets of gametes, leaving only f0*Ne for our mutations to spread in.) It is not reasonable to expect the Wikipedia reader to understand what equilibrium frequency refers to here. My interpretation is that it refers to the frequency of non-mutated gametes that is maintained by selection when a stream of deleterious mutations remove the other gametes. -- Ettrig ( talk) 21:58, 28 November 2009 (UTC)
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)
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)
Hmmm. This illustration/experiment seems overcomplicated. The process being decribed would seem essentially to be:
There are two colours of marbles in a group. 1. Choose one of these colours > Record your choice > Repeat x20. 2. Compare the proportions of colours in your record and the original.
From the article it seems that no more is being said than that the proportion of alleles in a future generation is determined by random selection as well as by natural selection. If this is the case, then rather than dive straight into abstruse mathematical expression, some real examples of this mechanism of chance (picking of the colour of marble for the new group) would help make the point better. LookingGlass ( talk) 08:02, 6 March 2014 (UTC)
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)
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)
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)
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)
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)
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)
This sentence The effect of genetic drift is larger for alleles present in a smaller number of copies, and smaller when an allele is present in many copies. is criticised. Copies of what? The answer is copies of alleles. When the question is posed, I think this could be interpreted as alleles in copies of something. We want to say When there are few copies of an allele, the effect of genetic drift is larger, and the effect is smaller when there are many copies. I came here to ask for help with the formulation. But I will try this and hope it provokes improvement. -- Ettrig ( talk) 06:23, 19 December 2011 (UTC)
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)
I've proposed a change to the lead sentence of the natural selection page, and I think a corresponding change should be made to the lead sentence of this page.
My proposed lead sentence for natural selection is "Natural selection is the differential survival and reproduction of individuals due to differences in phenotype."
My proposed lead sentence for this page is "Genetic drift is the differential survival and reproduction of individuals due to chance". (the reference can stay)
These edits would make the descriptions more accurate, and help highlight the parallels (and by doing so also the fundamental differences) between natural selection and genetic drift.
I can see that some sort of joiner sentence would need to follow; perhaps "From a genetic perspective, it can be defined as change in allele frequencies in a population due to chance." 129.127.101.245 ( talk) 06:05, 25 September 2015 (UTC)
I agree with Joanna on this - I wouldn't want to try to redefine the historical and accepted definition of genetic drift on this page. ( Aaronragsdale ( talk) 17:47, 29 September 2015 (UTC))
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)
"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)
This article was the subject of a Wiki Education Foundation-supported course assignment, between 23 August 2023 and 30 November 2023. Further details are available
on the course page. Student editor(s):
Amaner222 (
article contribs).
— Assignment last updated by RuthBenander ( talk) 14:05, 28 September 2023 (UTC)
“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)