Questions tagged [population-genetics]
Questions related to the study of the distributions and changes of allele frequency in a population.
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Books on population or evolutionary genetics?
I have recently been involved in collaborations that require me to model the population genetics of eukaryotic populations. I fear I may either be "re-inventing the wheel" or making conceptual ...
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Why is the strength of genetic drift inversely proportional to the population size?
I saw a concept on the Internet that says "the strength of genetic drift is inversely proportional to the population size". I don't know why they are inversely proportional? Can somebody explain? ...
user5407
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Do humans have enough biological differences to be grouped into races or subspecies?
After my online research on the subject, I learnt that, biologically speaking, many scientists believe that there is no such thing as a race. Homo sapiens as a species is only 200,000 years old, which ...
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Are mutations random?
The following claim
Mutations are random
or just the use of the expression
Random mutations
are very common among lay people.
The claim is very common among lay people. The claim is often ...
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Assumptions of Hardy-Weinberg rule
The post Solving Hardy Weinberg problems offers an easy explanation of Hardy-Weinberg rule. The current top answer explicitly does not talk about the assumptions of Hardy-Weinberg. A model makes sense ...
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How is genetic speciation defined?
What determines speciation at a molecular level?
At what point does a scientist determine two lineages are different enough to be considered separate species?
Does it have a margin of error?
sophie silec
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Why are the genomes of Humans 99.5% the same?
Human's DNA sequence is said to be roughly 99.5% equal. As far as I understand, this means that if I walked up to you and compared our DNA, the sequence of base pairs would be 99.5% the same.
My ...
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Did Darwin ever reach the conclusion that selection will remove variation?
According to simple models of selection the genetic variance in a population should be reduced by selection. (Fisher's fundamental theorem states that the rate at which a population can evolve is ...
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How to interpret the breeders equation?
The univariate breeders equation is defined as,
$\ R = h^2 s$
where $\ R $ is the response, $\ h^2 $ is the heritability (additive genetic variation), $\ s $ is the selection differential. The ...
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1
answer
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What is the percentage of people living in England in 1500 AD whose lineage is still alive?
This sounds a bit random, but it stems from a lecture in statistical genetics which I attended a while ago. We were shown a population lineage graph from which it was clear that most lineages ...
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Human genetic diversity in Africa in comparison with the rest of the world
Background
The claim ...
Most of the genetic diversity in humans is in Africa
... is quite common. On Biology.SE, it is easy to find posts that make this claim. Consider for example:
Do humans ...
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Why does the slope of parent-offspring regression equals the heritability in the narrow sense?
Background
---- Notations and assumptions ----
let $W_{ij}$ be the fitness associated to the genotype $AiAj$. $x$ is the frequency of the allele $A1$ in the population. The frequency of the allele $...
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How can someone share 50% of their DNA with their parents yet all humans share 99.9%?
I have heard that humans share 99.9% of their DNA with other humans. I have also heard that a child shares 50% of their DNA with their parents. How do I resolve this apparent contradiction? It has ...
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Genotypes in diploid/haploid cells under mitotic/meotic cell divisions
I am new to genetics , and am stuck with the following question at hand:
If $2$ cells with genotypes $(A/a)$ and $(A/a,B/b)$ undergo mitotic and meotic cell divisions respectively, what will be the ...
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Text Book Recommendation: Organic Evolution
I was wondering if anyone could point me in the direction of any text books on organic evolution? I have recently become interested in the subject and would like to know more. I think an undergrad ...
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Why didn't Escobar's hippos introduced in a single event die out due to inbreeding
Today I read a BBC Report about how Pablo Escobar had once imported 4 hippos (1 male, 3 female) into his estate in Colombia for his private zoo. After his downfall, while other species were shipped ...
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Effect of sex-ratio on the effective population size
As stated on this wikipedia article, the effective population size $N_e$ when the sex ratio differs from $\frac{1}{2}$ is
$$N_e = \frac{4N_mN_f}{N_m+N_f}$$
I understand the biased sex-ratio ...
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7
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1
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Easy derivation of Kimura's approximation for the probability of fixation of a mutation
Kimura's approximation for the probability of fixation of a mutation under selection finds recurrent use in population genetics models till date. I am trying to understand the mathematical basis of ...
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Variance in Fst in the infinite island model
The most famous result in the study of structured populations come from Sewall Wright. He showed that in an island model, where each subpopulation is of size $N$ and the migration rate is $m$, then ...
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Definition of "Effective population size"
Could you explain to me, what is the meaning of "Effective population size ($N_e$)"?
I would appreciate an example as well.
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Polymorphism in number of chromosomes?
The answer to this question, saying that Down Syndrome - a trisomy of human chromosome 21 - is caused by de novo mutation (rather than resulting from standing variation) made me think about ...
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How is it possible for the absolute fitness to be more than 1?
The wikipedia definition of Absolute fitness is "the ratio between the number of individuals with that genotype after selection to those before selection. It is calculated for a single generation and ...
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What are Codominant vs Dominant Genetic Markers?
When talking about types of genetic markers, the adjective "dominant" and "codominant" are often used. I don't fully understand their definitions and found contradicting definitions.
Foll and ...
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Why does the number of mutations per individuals follow a Poisson distribution?
I was reading this review. On page 11, left column, first paragraph, one can read:
[..] there is a Poisson distribution of the equilibrium number of mutations per individual, if fitness effects are ...
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How is "selection" best defined?
There is natural selection but there is also sexual selection which some regard as a category of natural selection. There is also artificial selection (by humans). The question is, what is a most ...
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What test to apply to detect genomic signatures of selection?
I would like to ask you for your sugestions for selecting a test to detect signatures of selection in the following mouse model:
We have three groups: animals exhibiting trait A, trait B and controls....
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answer
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What is a typical value of the selection coefficient s?
I am trying to gain an understanding of the real world effects of natural selection from the equations, especially comparing it with drift. However I have been unable to find any examples which give ...
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Why is the probability of fixation of an allele equal to its frequency?
Introduction
In a panmictic population, the probability of fixation of an allele at a neutral locus is equal to its frequency at that time. I will refer to this probability of fixation as calculated ...
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What are the consequences of inbreeding?
Inbreeding increases the risk of getting two identical recessive genes, alleles, that cause a disease which wouldn't have been activated with mixed genes. That's how I understand it anyway. But I ...
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Would a colony with only one male and female collapse?
This is a thought experiment:
If we form a population with only a single founder pair, can this population survive? What would happen? Would this inbreeding cause the population to go extinct? Could ...
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How to determine whether changes of an allele's frequency are due to genetic drift or selection?
Given that both natural/artifical selection and genetic drift are evolutionary mechanisms that influence how allele frequencies shift in a population:
Are there ways to determine whether a frequency ...
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Hamilton's derivation of direct fitness from his 1970 paper
In his 1970 paper "Selfish and Spiteful Behaviour in an Evolutionary Model", Hamilton uses Price's equation to derive his well-known rule $rb -c >0$. My question is about one of the steps in his ...
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Within and Between Allelic Class Diversity
I am reading Charlesworth et al. 1997. They talk about diversity within and between allelic classes.
Nucleotide diversities ($π$) at each neutral site were estimated from the mean of $2 \sum z_t (1-...
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Hill-Roberston effects and effective population size
From this article, first page, middle of the second column:
Even if harmful alleles do not become fixed, they can still reduce the efficacy of selection on neighbouring loci through a process ...
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Evolution of diversity and extinction resistance
I saw a comment on an answer to another question that touched on an interesting topic:
keeping diversity is useful for parameter exploration or to adapt to future environmental change
My initial ...
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Viruses in human history
How much do we know about ancient viruses and the viral evolution throughout the human history?
To my knowledge the HIV history has been rather well documented for about hundred years back (e.g., see ...
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Ways to distinguish between purifying selection and selective sweep
When looking a population genomic data, regions of low diversity (lower than expected; such as in a region of high recombination) can indicate either purifying selection of deleterious mutations or a ...
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Learn Bioconductor the hard way!
I came to analyzing population genetics data from the background of a theoretician and a computer biologist but not with the standard tools that a bioinformatician (or empiricist in population ...
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Coalescence time: Is it different for haploids and diploids in population genetics?
I'm trying to model Cyanobacteria cells divergence in 2 populations with mutation rate $-\mu$ and I need to verify my model with a valid theory. I don't have much biology background and all the ...
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How do I calculate the change in allele frequency in a haploid population under selection?
From this book
For simplicity, let us consider a haploid organism and assume that the frequencies of alleles $A_1$ and $A_2$ are given by $x$ and $y=1-x$, respectively. We also assume that the ...
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Initial population when I count backwards?
My question deals with the number of ancestors it took to produce me:
--> To produce me, it took 2 people (my parents) = ($2^1$) people = 2
--> One generation further included = ($2^1 + 2^2$) ...
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Is the variance of a trait related to its rate of evolution?
Posed with a question that has me stuck:
Is increased variance of a phenotypic trait in a population associated with slower evolution of that trait?
I have to either 'disagree or agree' and argue ...
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answers
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Interspecies competition and pathogen
Following my answer to this question, a debate ensued on whether the loss in population of one species (namely red squirrels) due to its lesser resistance to a pathogen brought by a competing species (...
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Outbreeding depression in humans [duplicate]
Is there any evidence of outbreeding depression in human beings?
user21998
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How could one calculate the gene flow between two populations?
Imagine there are two populations X and Y, and for each population you have the genotypes of each individual in that population (e.g. Aa, AA, aa, etc.), but for multiple loci (e.g. AABb).
How could ...
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Inbreeding Coefficient and Coefficient of Relationship
Wikipedia gives the following formula to calculate a "path of coefficient of relationship" between an ancestor $A$ and an offspring $O$:
$$\rho_{AO} = 2^{-n} \left( \frac{1+f_A}{1+f_O} \right)^{1/2} =...
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Identity By Descent vs Identity By State
Background
The concepts of Identity By Descent (IBD) vs Identity By State (IBS) are central in population genetics, yet I fail to fully wrap my head around the definitions.
You can find examples ...
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Isn't heritability more important to genic capture than just genetic variance?
Rowe & Houle (1996) give two criteria for the selection of costly female choice:
Condition dependence of sexually selected traits
High genetic variance in condition
Regarding heritability, ...
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How should one interpret heritability? Is it related to $R^2$?
From Wikipedia:
Heritability estimates are often misinterpreted if it is not understood that they refer to the proportion of variation between individuals on a trait that is due to genetic factors. ...
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Altruism in viscous (asexual) populations
The viscosity of a population is the tendency of offspring to remain
near their place of birth. Taylor 1992 ("Altruism in viscous populations") provides a model to study how viscosity affects the ...
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