39
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What would cause red-haired people to become fewer?
Let's consider a possible scenario, with a simplified assumption that red hair is a simple Mendelian recessive trait.
Let's say we have a population that is 10% red hair. Everyone with red hair lives ...
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37
votes
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Are mutations a source of genetic variation?
Going through the possible answers
(A) Rates tend to be very high in most populations.
This is a very unclear statement. What does "high" mean? In humans, the average mutation rate per ...
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29
votes
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Why didn't Escobar's hippos introduced in a single event die out due to inbreeding
I think one of the important things to understand in thinking about this case is that it just hasn't been that long, generationally.
Escobar imported the hippos in the late 1980s. Hippos reach sexual ...
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19
votes
What particular genetic mutations gave Europeans increased resistance to smallpox?
First, it is unlikely to be one specific mutation. Such strong selective pressures can lead to many forms of resistance.
Second, even for the mutations we suspect, smallpox is not a heavily studied ...
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15
votes
Discrepancy in time for genetic differences between human and chimpanzee to accumulate
Good literature work here and good question +1! In short, your main mistake was that you based your calculations on a single site and not on the whole genome. More info below.
Genome-wide vs sites ...
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11
votes
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Are mutations random?
Short answer
The claim is unclear but is essentially misleading and wrong. However, IMO, for lay people, it is a good approximation to just think that mutations are random!
Here, on Understanding ...
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11
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What particular genetic mutations gave Europeans increased resistance to smallpox?
None, because that's not how immunity works in the case of smallpox.
Most Europeans caught smallpox in childhood (or a variant; discovering that cowpox protected against smallpox led directly to the ...
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10
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How can someone share 50% of their DNA with their parents yet all humans share 99.9%?
It will be clear with a simple analogy.
You are 50% related to any one of your parent
Let's say you don't have any biology books. You have two friends, Alice and Bob. They each give you a copy of ...
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9
votes
What are the consequences of inbreeding?
You are right. Inbreeding strongly increases overall homozygosity which subjects inbred individuals to diseases caused by rare recessive alleles. In non-inbred individuals the chance is quite low to ...
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9
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Have there ever been "half-twins" who were halfway between siblings and twins?
Yes.
A case of semi-identical twins was reported in 2006. These twins share 100% of their maternal alleles and 50% for their paternal alleles. It's hypothesized this arose from a double fertilization ...
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8
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Understanding ancestry testing mathematically
I'll give here a simple, non-technical answer because I'm assuming you don't need to actually perform an analysis of ancestry.
So, detecting ancestry is a non-trivial task. Given your genome ...
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8
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Why didn't Escobar's hippos introduced in a single event die out due to inbreeding
They often do. You hear a lot about all of the times invasive species succeed in invading a new habitat, because there is a surviving population around for researchers to observe. There are lots of ...
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7
votes
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Human genetic diversity in Africa in comparison with the rest of the world
Here is a tree based on mitochondrial DNA variations in human populations.
van Oven M, Kayser M. Hum Mutat. 2009 Feb;30(2):E386-94.
Updated comprehensive phylogenetic tree of global human ...
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7
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Why didn't Escobar's hippos introduced in a single event die out due to inbreeding
There are some references on this: Castelblanco-Martinez, 2021 is a recent one. There doesn't seem to be much doubt at least that hippopotami are thriving as an invasive species.
I didn't see ...
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7
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How exactly do mutations cause genetic variation in bilaterians?
For example, does the mutation need to occur in the DNA of either the specific sperm or the specific egg that gave rise to you?
To give rise to heritable genetic variation in the sense that it's a ...
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6
votes
Text Book Recommendation: Organic Evolution
Organic Evolution - Definition
'Organic evolution' was a common term. It is just rarely used today. Today, we just say 'evolution' or 'evolutionary biology' when referring to the field of study of '...
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6
votes
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Can the apparent drop in insect population be explained by local insects evolving to avoid traps?
From your own PlosOne link comes proof that the selection pressure was very weak:
"Most locations (59%, n = 37) were sampled in only one year, 20 locations in two years, five locations in three years, ...
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Why didn't Escobar's hippos introduced in a single event die out due to inbreeding
To focus on the inbreeding:
Inbreeding in itself is not a factor that would make species die out. Rather, inbreeding increases the risk of genetic diseases, if the deleterious alleles are already ...
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6
votes
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Viruses in human history
We don't know a whole lot about the direct evolution of the genomes of many viruses yet, though as methods for recovery of ancient nucleic-acid sequences improve, I would expect to see increases in ...
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6
votes
Why isn't speciation a negative feedback loop?
I'd suggest looking at this article, which contains an intuitive model for how hybrid incompatibilities can arise between isolated sister taxa (i.e. populations). This criterion of pre-existing ...
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6
votes
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How can I find/simulate mixed-ancestry DNA data?
Price et al 2009 describe how to simulate admixed genomes in this paper.
We constructed 40 haploid admixed genomes (n = 1 to 40) from the 40
haploid Yoruba and 40 haploid French genomes by using ...
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5
votes
Outbreeding depression in humans
Answer below is copy-pasted from the section Do we have documented cases of outbreeding depression? of my answer here.
Many cases of inbreeding depression have ...
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5
votes
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Assumptions of Hardy-Weinberg rule
Here are the assumptions to the standard Hardy-Weinberg rule (HWr) formulation
$$p^2 + 2p(1-p) + (1-p)^2 = 1$$
See Solving Hardy Weinberg problems for more info about this formulation.
Assumptions
The ...
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5
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What are the consequences of inbreeding?
There is indeed evidence that inbreeding in humans lowers intelligence of offspring.
In summary, our comprehensive assessment revealed that parental consanguinity and degree of inbreeding was ...
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Human genetic diversity in Africa in comparison with the rest of the world
I've found two papers that provide some information on this, but no definitive answer.
The 1000 Genomes Project Consortium (2015) analysed whole genomes and found that "28% of novel variants" were ...
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About lack of selective pressure
Often the phenotype caused by a given allele depends on the alleles present in other genes; this is termed epistasis. In the context of tumors, selective pressure is primarily associated with the ...
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5
votes
Are mutations a source of genetic variation?
Mutations are one of multiple reasons for genetic variation, hence phenotypic variation. By definition, mutations are alterations of genetic code and unpredictable changes in nucleotide sequences {in ...
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votes
Population Genetics Using WGS: How do I know when I have enough individuals?
I think that many of the applications that you mention require wildly different numbers of individuals. It would help to know more about goals, questions, organism details, etc.
For example, for ...
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5
votes
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Disease-causing allele frequency and modern medicine
Yes, in principle, but it could take a very long time. Consider phenylketonuria, which is a severe genetic disease that is completely preventable by excluding phenylalanine from one's diet. Suppose ...
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