Questions tagged [population-genetics]
Questions related to the study of the distributions and changes of allele frequency in a population.
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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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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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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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Are mutations a source of genetic variation?
Here is a question from the book SAT II Success Biology E/M (where the SAT is the exam taken by the American high school students):
Which of the following statements is true about mutations?
(A) ...
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What would cause red-haired people to become fewer?
There is this misconception that red-haired people are going to die out. This person on the Internet ("howstuffworks") also connected it to a marketing campaign of a hair dyer company. But I'...
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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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Do men have a higher genetic variance than women?
I've heard that with the distribution of our genome women have less variation on the bell curve than men.
Is there any basis for this? It was my understanding that women have more genetic variation ...
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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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Discrepancy in time for genetic differences between human and chimpanzee to accumulate
Genetic differences between human and chimpanzee include ~50,000 amino acid changes, ~30,000,000 point mutations in non-coding sequences, and millions of insertions, deletions, inversions, genomic ...
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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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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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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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Expected time for a neutral allele to reach a frequency of $p_1$ when starting at frequency $p_0$
Kimura and Ohta (1968) showed that the expected time for a neutral allele to reach fixation (given that it will reach fixation) is
$$\bar t(p_0)=-4N\left(\frac{1-p_0}{p_0}\right)\ln(1-p_0),$$
where ...
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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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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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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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Is it mostly true that predators or parasites traverse wider spatial areas than their prey or hosts?
Does it tend to be true that as you go up the food chain, the species tend to cover wider areas? I am basically asking whether a population's prey varies spatially more than a population's predators ...
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How to define "Quasifixation" in continuous approximation of finite population?
Background
Many models including the famous very first models derived by Sir Ronald Fisher in his early career, assume infinite population size. In an infinite population, an allele can rise in ...
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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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Term for trait that is advantageous to a population only as long as it is rare
I remember reading about a concept—in evolutionary biology or natural selection, I think—whereby a particular trait is advantageous to the population or species but only so long as that trait is only ...
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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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What is the minimum population size that Hardy-Weinberg calculations can be applied to?
I'm trying to find out if a particular allele is in Hardy-Weinberg disequilibrium, but the data is poor. What's the minimum population number that you can use to get any sort of respectable conclusion?...
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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 I find/simulate mixed-ancestry DNA data?
Some collaborators and I are building an ancestral inference tool, and we're having trouble obtaining reliable ground-truth data for samples of mixed ancestry. All the ground-truth DNA datasets we're ...
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Mathematical models of lineage selection
I'm interested in the concept of lineage selection (Aboitiz, 1991) as an explanation for why traits would be selected for that enhance the rate at which evolution can occur, rather than directly ...
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Help with the Price equation
The Price equation describes mathematically the evolution of a population of units from one generation to the next.
$\bar{w}\Delta \bar{z}$ = $Cov (w_i,z_i) $+$ E(w_i\Delta z_i)$
I would like to ...
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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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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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Hamilton's inclusive fitness approach
The underlying intuition of Hamilton's model of inclusive fitness is that we should study social behaviors from the point of view of actors -- rather than the recipients. To build his model, Hamilton ...
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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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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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Why are recombination rates increasing in mammals?
I have recently become fascinated with an awesome topic in biology and evolution that I feel is rarely covered in biology courses. That is, rates of meiotic recombination, or the the amount that an ...
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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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Understanding F-statistics in population genetics
I am reading the classic Weir and Cockerham 1984 paper about $F_{ST}$ estimation. At the beginning (first page, right column), they define 3 statistics.
$F$ is the correlation of genes within ...
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What does "Mutational Variance" mean?
Background
The concept of mutational variance can be found in many articles including this one for example. The mutational variance of a trait number $i$ can be found in the M-matrix in position $m_{...
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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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Average and lowest degrees of kinship/consanguinity among humans?
I would appreciate insight into the average, median, RMS or any similar measure of relatedness among the current world population - and perhaps something about how rapidly this may be changing. A ...
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Why is there no symmetry in pigmentation when comparing people north and south of the equator?
If you are at the equator and start moving north, the further you travel, the lighter the skin of the indigenous peoples. Considering that we live on a ball, why do we not find the same traveling ...
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How to seek for available genetic data relevant to ecology and evolution?
I had a quick look online. There seems to exist many different website of database archiving. Some data might be free of charge while some others might not be. I found things such as Dryad, TreeBase, ...
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What is Environmental Robustness? Is it different from plasticity?
Hansen (2006) in his review uses the concept of environmental robustness independently of the other concepts of robustness (at pages 139 and 140) without defining ...
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Diffusion approximation to genetic drift
I am reading from the classical textbook Principles of Population Genetics, Hartl and Clark (pdf here).
Introduction
Let $f(p,x,t)$ denote the distribution of allele frequency $x$ at time $t$ ...
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Recommendations for textbooks on statistical and quantitative genetics, and genetic epidemiology
I'm looking for a textbook on statistical genetics, quantitative genetics, association mapping, and genetic epidemiology. My interests include, but are not limited to, complex trait analysis, and the ...
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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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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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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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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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Do mutant alleles result from mutation of the wild type?
The allele that encodes for the most common form of a phenotype in natural population is called a wild type allele and all the rest of the alleles encoding forms other than the wild type are called ...
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Understanding ancestry testing mathematically
Forgive me if this question has been asked here before, because it is something which should be very easy to find, but I can't seem to find an answer no matter where I search.
The question is simply ...
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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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