Questions tagged [population-genetics]

Questions related to the study of the distributions and changes of allele frequency in a population.

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Identity by descent among unrelated individuals

I was reading a couple of papers which talk about IBD (Identity by descent) among unrelated individuals (for eg. http://www.pnas.org/content/109/4/1193.long). However they do not seem to clearly ...
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116 views

How frequent are selective sweeps?

Introduction Selective sweep is the most famous genetic signature of selection. We know of a number of classical examples of selective sweeps, some of them in humans. See the classical example of the ...
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177 views

How does the population fitness change after a change in mutation rate?

The mean population fitness as given by mutation load theory depends only on the genome-wide mutation rate ($U$). My question is: How many generations is needed to reach a new mutation load ...
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110 views

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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1k views

Mutation-Selection-Drift Equilibrium

mutation-selection-drift equilibrium is one of the most important concept of population genetics. I could easily find the calculations for mutation-secltion equilibrium and for mutation-drift ...
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104 views

How does the new discovery that mitochondrial dna is inherited from both parents change population genetics and other dates?

This new study seem to have pretty much proven that mtDNA is inherited from both parents. I assume that this would lead to most age estimates of ancient human ...
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47 views

Offspring of parents with different number of chromosomes

Many papers report that dog-whelks (Nucella lapillus) show a distinct chromosomal polymorphism between populations of 2n = 24 up to 2n = 36. Could somebody please tell me how many chromosomes the F1 ...
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79 views

How to choose the most appropriate measure of genetic distance

I am conducting a phylogeography study of a fish species and am trying to construct a phylogenetic tree to describe population structure and ancestry. I have constructed trees using various measures ...
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91 views

Why does my simulation not support the idea that inbreeding is bad?

After reading this post, I wrote some code to simulate inbreeding. We have a population of $N$ creatures. Each creature has two genes, which come in two forms: recessive (a) and dominant (A). The ...
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1k views

Are epicanthic folds a dominant trait?

My state (Tripura) originally had a mostly mongoloid-feature-possessing population (ethnic group: Tripuri). Recently a large number of non-mongoloid people (ethnic group: Bengali) have migrated to ...
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110 views

What is the effective population size of a simple two deme metapopulation?

I am confused as to how to compute the effective population size $N_e$ of a theoretical structured population. Let's consider here a simple case study. Imagine a 2-deme metapopulation. Each deme is ...
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251 views

Population size and genetic drift - What are the evidences?

Wright-Fisher model From the Wright-Fisher model of genetic drift, the random sampling of allele from one generation to the next is taken from a binomial distribution with parameters $2N$ and $p$, ...
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315 views

Runs of homozygosity - degree of inbreeding and disease associations

Been reading recently about methods to determine how inbred a particular person is by measuring their "runs of homozygosity." Loosly, these are defined as regions of the genome (typically >1Mb) where ...
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110 views

Is $F_{ST}$ a probability and a correlation coefficient?

$F_{ST}$ is one of the most famous and most important statistics of all of evolutionary biology. Yet, many people misunderstand it or misuse the classical results from the literature on $F_{ST}$ (...
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174 views

How to understand relatedness in an infinite island model?

My understanding is that the relatedness coefficient in kin selection models measures positive assortment. That is, altruism is more likely to evolve if altruists tend to interact with other altruists....
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157 views

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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39 views

What the “due to” means in the definition of heritability?

According to Wray and Visscher, heritability is formally defined as the proportion of phenotypic variation (VP) that is due to variation in genetic values (VG). My question is, what does “due to” ...
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113 views

what is the difference between homozygous and heterozygous duplication?

In a genetic test result it's written homozygous duplication or heterozygous duplication Does it mean four copies of the ...
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19 views

Is there an existing database of mutation rates for mitochondrial loci?

I'm wondering if there exists a database of mutation rates (transitions and transversions) for both mitochondrial loci (such as cytochrome c oxidase subunit I (COI)). Due to the use of COI as a DNA ...
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29 views

Estimating population divergence time with a single mitochondrial marker

Is it possible to estimate population divergence time with a single mitochondrial marker? Here is additional information for my specific case: Mitochondrial marker: Cytochrome Oxidase Subunit 1 (...
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48 views

Appropriateness of PCA to visualize clusters in genetic data

In many genetic studies, PCA is often utilized to examine genetic cluster in human populations. Rarely is the % variance reported for the components. With human data it's been my experience that the ...
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26 views

How does one go from a couple of DNA sequences to a distance-matrix?

For a project we need to explain the subject of UPGMA. We think we understand thee method itself but I fail to see how you go from a number of DNA-sequences to the distance matrix. I understand ...
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55 views

How do I solve this problem related to specificity and sensitivity?

Consider an autosomal recessive disease with an incidence of 1/10,000 in the general population of 100,000. Your best friend comes to you very upset because he has just taken a screening test for this ...
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234 views

Infinite site model and Watterson's Estimator

Why is it that under migration, the watterson's estimator (theta) is upward biased? What does upward bias means? And why do we have downward bias under exponential growth? Lastly, is it only the ...
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141 views

How to tell if/how allele frequencies change (USABO question)

This is question number 34 from the 2014 USABO Open Exam: Black and white mice live on an island and have allele frequencies of B=0.20, b=0.80. On the continent, there is a much large population of ...
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49 views

What model of epistasis best fit the reality?

In theoretical population genetics, it is very common to have to assume a model of epistatic interaction. The two most common models are the additive model and the multiplicative model. Additive ...
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301 views

Variance in reproductive success and effective population size

Background The effective population size $N_e$ is the size of the Wright-Fisher population that experience the same amount of drift than the population under consideration. The higher the variance ...
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119 views

Efficient algorithm to calculate various population divergence statistics

Intro and description of the data I am simulating the evolution of very long DNA sequences. The model works well, is performant and will output data in the following kind of fasta format ...
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194 views

Falconer & Mackay population mean calculation & genotypic values

I am reading chapter 7 of Falconer and Mackay where they give a formula to calculate the population mean as a deviation from the heterozygote genotypic value. As an example, imagine a one locus two ...
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57 views

Analytical Methods for Estimating Probability of Fixation

The probability of fixation $P$ of an allele is an very important measure and there exists several solutions to estimate this probability. Each method has its own assumptions and it is often hard to ...
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177 views

What is the probability of fixation for a mutant under fluctuating selection?

Here is an answer which explains how one can model the frequency of an allele that is under fluctuating selection (the selection that varies through time). Not, thinking about fluctuating selection, ...
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131 views

$F_{ST}$ when considering a multi-allelic locus

Sewall Wright defined the $F_{ST}$ in a metapopulation as being: $$F_{ST} = \frac{\text{Var}(p)}{\bar p (1-\bar p)}$$ , where $p$ is a vector of frequencies of a given allele and $\bar p$ and $\text{...
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25 views

What is the distribution of gene polymorphism levels across human genes?

Of the approximately 19,000 human genes, about how many have one allele that occurs with appreciable frequency in the current human population, how many have two alleles, and so on? (By "appreciable ...
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27 views

Finding intensity of selection against dominant homozygotes

I was looking at some Olympiad questions and came across the following: If the frequency of a completely recessive allele is $0.2$ and it remains unchanged from generation to generation due to ...
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51 views

Balancing selection vs introgression?

Balancing selection can maintain polymorphisms in natural populations for extended periods of evolutionary time. However, in this paper, Dannemann et al. 2016 identify three archaic haplotypes in the ...
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34 views

Can Tajima's D and other population genetic tools be used to copare Arabidopsis ecotypes?

I am currently investigating 2 genes in Arabidopsis taliana that are a product of a recent duplication even (observable from synteny and phylogenetic analysis). In addition to the molecular and ...
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25 views

Does consistency in minor allele frequency of a SNP across populations imply selection?

If a particular SNP has very similar MAF value across multiple largely non-overlapping populations, with the assumption of no gene flow between the populations over many generations, would that then ...
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47 views

Monohybrid Recombinant Frequency? (three point Gene Linkage)

I am curious to know if it is completely impossible calculate recombinant frequency for monohybrids ( three point link, gene map etc.) Here is an example: Marker 1 xx= 25 xy=100 yy= 20 Marker 2 ...
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35 views

Measuring genetic distance: $F_{ST}$ vs. Nei's distance

As far as I'm aware, Nei's genetic distance is quite old compared to $F_{ST}$. However, I have recently read more papers that utilized Nei's genetic distance alongside with $F_{ST}$. As I'm not very ...
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30 views

The concept of high genetic load of disease and non-random segregation of deleterious variants

I'm new in this field. I was reading Shakeel et al. (2018) and came across the below sentences The rate of emergence and distribution of deleterious variants in populations is important in ...
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15 views

Gene flow analysis with a single mitochondrial marker

I am currently studying a mud snail genus called Ecrobia. Several species of this genus occur in both the Mediterranean and Black seas. Therefore, I would like to investigate whether there is: ...
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Is there any data to explore the heterozygosity of the South African lion over the last 18 years?

Background: I need to find data on the heterozygosity of the south African lion over the last 18 years... and I'm struggling: so far I have found a single data point. Question: Where can I find ...
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159 views

Coefficient of relatedness for a locus on the Z chromosome

So i know that the ZW determination system is the equivalent for XY in birds. Moreover, I know that the coefficient of relatedness between siblings for the X chromosome is 0.5 so im guessing that the ...
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69 views

How can census population size be smaller than the effective population size in some species? is that possible?

The only way I can think this could happen is through a recent population bottleneck. Can it be possible though ?
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29 views

How does one calculate Rx/a in population genetics?

The ratio of sex-linked to autosome mutation frequencies (R) is Rx/a =(2/3)(2+ α)/(1+ α) for X-linked genes and Ry/a = 2 α /(1+ α) for Y-linked genes. How does one calculate Rx/a, in order to find α?
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2answers
460 views

How to interpret McDonald-Kreitman test results?

It is easy to get the numbers right and calculate neutrality index. It is easy to memorize "equals", "greater", "lesser", etc. At least on the exams, when certain level of simplicity is assumed. But ...
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42 views

Use numbers or algebra when introducing an evolutionary biology concept?

I'm working on an (approximately 20 pg) evolutionary biology paper for submission to a journal. The paper introduces a couple of strategies (I use "strategies" loosely; they can be carried out by ...
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47 views

Replication cohorts in microbial GWAS

Replication in an independent cohort is of course the gold standard in GWAS studies, and many high profile journals will now (quite rightly) not accept finding indicating a phenotype genotype ...
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61 views

What is Hamilton's rule for multiple generations?

What is Hamilton's rule as it applies to multiple generations? Is it that the lineage success given up by the actor must be exceeded by the lineage success acquired times the relatedness between ...
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406 views

Can the value of heritability be greater than 1?

Heritability defined as genetic variance divided by total variance seems to be bounded between 0 and 1. However, I see a way of calculating heritability on this page (http://www.radford.edu/~rsheehy/...