Posts Tagged: Genetics

Uncategorized — No Comments
19
Jan 10

Dog Genetics and Domestication

Interesting study on the genetics of dogs. The comparisons they are making with dog domestication and recent evolution in humans is interesting.

Although domestication of dogs began over 14,000 years ago [...] the spectacular diversity among breeds is thought to have originated during the past few centuries through intense artificial selection of and strict breeding for desired characteristics. [E]ffort[s] [are underway] to map canine genome regions that show signs of recent selection and that contain genes that are prime candidates for further investigation. Those genes are being examined for their possible roles in the most conspicuous variations among dog breeds: size, coat color and texture, behavior, physiology, and skeleton structure.

The researchers performed the largest genome-wide scan to date for targets of selection in purebred dogs. The genomes came from 275 unrelated dogs representing 10 breeds that were very unlike each other. The breeds were: Beagle, Border Collie, Brittany, Dachshund, German Shepherd, Greyhound, Jack Russell Terrier, Labrador Retriever, Shar-Pei, and Standard Poodle.

The study was conducted, the researchers said, because the canine genome, the product of centuries of strong selection, contains many important lessons about the genetic architecture of physical and behavioral variations and the mechanisms of rapid, short-term evolution. The findings, the researchers said, “provide a detailed glimpse into the genetic legacy of centuries of breeding practices.”
[...]
Their list of most differentiated regions of the dog genome included five genes already linked to hallmark traits of certain breeds: one for small size, one for short limbs like those in Dachshunds and other stubby-legged dogs, and three for coats.
[...]
A major impetus behind studying dog genomics, the researchers pointed out, is its potential to advance knowledge about the genetic basis of human form variations and of differences in disease susceptibility among people. In many cases, the researchers said, it may be easier to locate the genetic targets of selection in dogs, and then map these to related regions in the human genome. Scientists are intrigued by the possibility that recent selection may have affected genome regions common to both human and dog lineages.

“This research has shown that artificial selection in dogs has acted on many of the same genes as natural selection in humans, and that many of these genes are regulators of gene activity,” [...]

The researchers also said that a better understanding of artificial selection in dogs may reveal the molecular mechanisms of rapid, short-term evolution. Future work, they hope, may uncover the gene activities responsible for shaping the incredible diversity among the world’s dogs.

(Emphasis mine.)

(Link)

Uncategorized — No Comments
11
Jan 10

Depigmented Lizards and MC1R

Fans of Genetics will know the gene MC1R plays a role in human depigmentation, and even, as it seems, Neanderthals too. Well it looks like the same gene is also involved in depigimentation in 3 types of lizards. Here is what Ed Young has to say about the lizards…

In the White Sands National Park of New Mexico, there are three species of small lizard that all share white complexions. In the dark soil of the surrounding landscapes, all three lizards wear coloured coats with an array of hues, stripes and spots. Colours would make them stand out like a beacon among the white sands  so natural selection has bleached their skins. Within the last few thousand years, the lesser earless lizard, the eastern fence lizard and the little striped whiptail have all evolved white forms that camouflage beautifully among the white dunes.

(Link)

One of the interesting things (besides the convergent evolution going on here between humans and lizards) is that the 3 different lizards’ mutations on the MC1R gene are all different.

Uncategorized — No Comments
11
Jan 10

Moral Foundation Theory and U.S. Politics

Jonathan Haidt and Joshua Knobe talk about Moral Psychology and Moral Foundation Theory as it applies to U.S. politics.

(Link)

Uncategorized — No Comments
9
Jan 10

Altruism and Genetics

Some things to keep in mind from Greg Laden…

The appearance of altruism [in nature] is usually underlain by selfish motives.

The bottom line is this: A variant of a gene (an “allele”) that confers a trait that results in group-level or species-level survival or reproduction at the expense of the individual will have lower fitness than an allele that instead confers a trait that results in individual survival or reproduction.

Uncategorized — No Comments
9
Jan 10

Genetic Discontinuity Between Hunter-Gatherers and Central Europe’s First Farmers

Yann Klimentidis is back blogging again with a new post about the “Genetics of hunter-gatherers and early farmers in Europe” where he talks about the paper “Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe’s First Farmers“.

An interesting paper in that it suggests today’s Europeans are not (primarily) descendant from the original Europeans. (Although I think more evidence is needed before a convincing argument can be made for this.)

Yann’s comments on it are as folllows…

They examine the Fst in mtDNA sequence between hunter-gatherer samples (13,400 to 2,300 ago) in Central Europe, from more recent individuals (and modern Europeans). I guess they must use archaeological or other evidence to determine their subsistence pattern.

They get an Fst of 0.163, which is indeed remarkably high – although do we really know what to expect when comparing populations over time? To answer this, they perform some simulations, and reject the hypothesis that this Fst could have been due to a process of population continuity.

Along with their discussion of the haplotype differences betwee[n] the hunter-gatherers and farmers, this result is pretty interesting and suggests a migration of early farmers into central Europe and replacement of hunter-gatherers.
Proto-Indo-Europeans?

(Emphasis mine.)

Uncategorized — No Comments
8
Jan 10

Link Between Schizophrenia and Brain Efficiency

One of the most devastating types of mental illness could be a by-product of the evolution of human beings’ uniquely sophisticated intelligence, a new genetic study has suggested.

Scientists have discovered that a common version of a particular gene appears both to enhance a key thinking circuit in the brain, and to be linked to a raised risk of schizophrenia.
[...]
In the study, the NIMH team examined a common variant of a gene called DARPP-32. Three quarters of the subjects studied had inherited at least one copy of the variant.

This common version of the gene appears to make the brain’s most sophisticated thinking region more efficient, the researchers found. It improves the way that information is exchanged between the striatum, a brain region that processes reward, and the prefrontal cortex, the brain’s executive hub that manages thoughts and actions.

When this circuit works efficiently, the normal outcome is more flexible thinking and improved working memory. As a result, genes such as DARPP-32 that enhance it have probably been favoured by evolution.

The same circuit, however, has also been linked to brain functions that go wrong in patients with schizophrenia. [...]

(Emphasis mine.)

(Link)

Uncategorized — No Comments
7
Jan 10

Introgression of Brain Size Gene Microcephalin into Homo Sapiens from Archaic Humans

An interesting are of study in human genetics is the notion of introgression. That modern homo sapiens may have genes may have genes from other archaic human groups. Like Neanderthals.

Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage
Abstract

At the center of the debate on the emergence of modern humans and their spread throughout the globe is the question of whether archaic Homo lineages contributed to the modern human gene pool, and more importantly, whether such contributions impacted the evolutionary adaptation of our species. A major obstacle to answering this question is that low levels of admixture with archaic lineages are not expected to leave extensive traces in the modern human gene pool because of genetic drift. Loci that have undergone strong positive selection, however, offer a unique opportunity to identify low-level admixture with archaic lineages, provided that the introgressed archaic allele has risen to high frequency under positive selection. The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens. Within modern humans, a group of closely related haplotypes at this locus, known as haplogroup D, rose from a single copy ≈37,000 years ago and swept to exceptionally high frequency (≈70% worldwide today) because of positive selection. Here, we examine the origin of haplogroup D. By using the interhaplogroup divergence test, we show that haplogroup D likely originated from a lineage separated from modern humans ≈1.1 million years ago and introgressed into humans by ≈37,000 years ago. This finding supports the possibility of admixture between modern humans and archaic Homo populations (Neanderthals being one possibility). Furthermore, it buttresses the important notion that, through such adminture, our species has benefited evolutionarily by gaining new advantageous alleles. The interhaplogroup divergence test developed here may be broadly applicable to the detection of introgression at other loci in the human genome or in genomes of other species.

(Emphasis mine.)

(Link)

Uncategorized — No Comments
7
Jan 10

We Are 8% Virus?

It’s nothing new that DNA can get transmitted by virii, so this shouldn’t be a surprise….

About eight percent of human genetic material comes from a virus and not from our ancestors, according to researchers in Japan and the U.S.
[...]
The research showed that the genomes of humans and other mammals contain DNA derived from the insertion of bornaviruses, RNA viruses whose replication and transcription takes place in the nucleus.
[...]
The assimilation of viral sequences into the host genome is a process referred to as endogenization. This occurs when viral DNA integrates into a chromosome of reproductive cells and is subsequently passed from parent to offspring. Until now, retroviruses were the only viruses known to generate such endogenous copies in vertebrates. But Feschotte said that scientists have found that non-retroviral viruses called bornaviruses have been endogenized repeatedly in mammals throughout evolution.

(Link)

Uncategorized — No Comments
6
Jan 10

Camels vs Roads

A reoccurring theme in many fields of study (such as economics, genetics, memetics, and others) is that no one will ever have enough information to centrally plan things. The book “The 10,000 Year Explosion” provides another example of this….

Somewhere back in late classical times, the use of the camel was perfected — a better saddle was developed, for example, one that allowed camels to carry heavy leads efficiently. Throughout most of the Middle East and North Africa, camels were (after those developments) a superior means of land transportation: They were cheaper than ox-drawn wagons and not dependent upon roads. Over a few centuries, people in areas where camels were available abandoned wheeled vehicles and roads almost entirely. You can still see the effects in the oldest sections of some cities in the Arab world, where the alleys are far too narrow to have ever passed a cart of wagon. Europeans, not having camels, had to stick with wheeled vehicles, which were clearly more expensive, given the infrastructure they required. But as it turned out, wheeled vehicles — in fact, the whole road/wheeled vehicle system — could be improved. Back then, when the camels seemed so much better, who knew that someday there would be horse collars and nailed horseshoes, then improved bridge construction, suspensions that reduced road shock, macadamized roads, stream power, internal combustion engines, and ultimately the nuclear Delorean. The motto here is that sometimes the apparently interior choice has a better upgrade path [...]

Or put another way, the “invisible hand” tends to perform better than any form of central planning.

UPDATE: This passage was sourced from the book: “The Camel and the Wheel”, by Richard W. Bulliet.

Newer Entries →