genetics
razib | June 14, 2007Ruchira Paul sent me an email asking me to clarify this exposition of how gene selectionism can explain 50:50 sex ratios. First, I would like to second the author of the original post's injunction to read Richard Dawkins' The Selfish Gene, it is a masterpiece of scientific exposition. For many people an encounter with the The Selfish Gene is a K-T scale event, the world is changed after the encounter. That being said, it surely isn't the last word. A friend of mine mentioned how she noted that Dawkins heaps scorn on Amotz Zahavi's Handicap Principle, but a generation later this model has…
razib | June 13, 2007There's a new paper in Nature (OPEN ACCESS), Identification and analysis of functional elements in 1% of the human genome by the ENCODE pilot project:
...First, our studies provide convincing evidence that the genome is pervasively transcribed, such that the majority of its bases can be found in primary transcripts, including non-protein-coding transcripts, and those that extensively overlap one another. Second, systematic examination of transcriptional regulation has yielded new understanding about transcription start sites, including their relationship to specific regulatory sequences and…
razib | June 11, 2007There is a somewhat confused piece in The New York Times about eugenics for dogs today. I say confused because the article offers various cautions, but connecting the dots from the facts littered throughout suggest easily why the cautions aren't warranted. One of the big issues lurking throughout the article is that of pleiotropy and correlated response, pretty important factors in directional evolution.
The logic is simple, if a gene, A, has a quantitative impact on traits 1-100, selecting that gene specifically in the context of trait 23 will have unforeseen consequences for the 99 other…
razib | June 8, 2007First, check out this quick primer on genetic association studies. With that, Combined Genome Scans for Body Stature in 6,602 European Twins: Evidence for Common Caucasian Loci @ PLOS. You need such huge sample sizes to pick up the relatively weak singals from numerous quantitative trait loci. The study reiterates the finding that height is about 80% heritable, that is, 4/5ths of the population wide variation is due to genetic variation. At least amongst whites in the modern world (where nutritional deficit is minimized). That being said, though plenty of potentialities lurk beneath the…
razib | June 6, 2007Nature today published a paper which reports on a massive genome association study of the British white population with the intent of smoking out loci implicated in disease. The paper is open access, so you can read it yourself! There are many popular press articles, but as usual p-ter has a summary of the important points.
razib | June 6, 2007John Hawks points me to this story in The New York Times about research to be published in PNAS. Basically the researchers found that chickens buried in south-central Chile about a century before the Spanish contact with the New World were genetically most similar to those from Polynesia. This is a pretty obvious case for pre-European contact between Old and New World peoples.
Frankly, on a priori grounds this is a no brainer, if Polynesians could make to Easter Island it seems implausible that continental South America would be too far. Also, there is historical documentation which…
purepedantry | June 6, 2007You would think that language as a general phenomena in the human species is genetically prescribed, but the peculiarities of individual languages -- such as whether a people uses a particular phoneme or not -- is the result of historical or geographical factors.
Dediu and Ladd, publishing in PNAS, have shown that is true with one exception: whether the language spoken by a population is tonal or not may be related to the genetic structure of that population. (A tonal language is one in which particular phonemes can mean different things depending upon the tone in which they are spoken. An…
razib | June 4, 2007p-ter has an excellent review of a new paper, Localizing Recent Adaptive Evolution in the Human Genome. Imagine if you will a flat pristine stretch of snow covered field which exhibits a perfect 2-dimensional symmetry. Now, note what happens when a few snow blowers criss-cross the field. That's the sort of thing I imagine when attempting to analogize selective sweeps going through human populations over the past few tens of thousands of years. Money shot:
...In general, we find that recent adaptation is strikingly pervasive in the human genome, with as much as 10% of the genome affected by…
evolgen | June 3, 2007There are two genetics blog carnivals available for your perusing today. First is Gene Genie hosted by Hsien at Eye on DNA. The second is Mendel's Garden, over at The Daily Transcript. Hsien will also be hosting the next edition of Mendel's Garden. Visit the Mendel's Garden webpage if you'd like to contribute to the next edition.
grrlscientist | June 3, 2007Another (relatively) new blog carnival, known as Mendel's Garden has just published its 15th edition for you to enjoy. This blog carnival focuses on the interplay between genetics and the environment, and they included two entries that I wrote in their list (of course, this makes me happy).
evolgen | June 3, 2007Let's go through the basics again. Cracking the genetic code refers to figuring out how DNA encodes the information to make proteins -- that was done decades ago. Sequencing a genome does not mean that you have decoded the genome; presumably, decoding a genome would mean you've figured out the function of every part of a sequenced genome, but there really isn't a proper definition. In genetics, mapping refers to determining the location of genetic elements, which is different than sequencing. And deciphering has no real meaning.
With that said, check out the newest New York Times article on…
clock | June 2, 2007Evolution of direct development in echinoderms
It's been several years since I last heard Rudolf Raff talk about his work and apparently he's been busy in the meantime. The new stuff is exciting, and PZ knows how to explain it really well.
razib | June 1, 2007Tonal languages, ASPM, and MCPH. Over at my other blog p-ter reviews the paper now that it is out in PNAS.
razib | May 31, 2007OK, most of you know some genetics. You know that immunological profiles are very diverse, and you know that because of the mathematics of this diversity matches aren't easy. The problem increases in magnitude when you can not look within your ancestral population because the combinations will tend to draw from the modal alleles within that population. If that isn't clear: many small minorities in the United States are faced with the prospect of very long odds when it comes to tissue matches because of low numbers. This means proactive drives are necessary, as a matter of life & death…
grrlscientist | May 30, 2007tags: cheetahs, evolution
Researchers studied 47 litters of cheetah cubs over nine years. Nearly half contained cubs from multiple fathers.
Image: Sarah Durant [larger]
DNA technology has revealed that female cheetahs, Acinonyx jubatus, often produce litters that are comprised of cubs sired by multiple fathers. This research, recently published in the Proceedings of the Royal Society B, studied cheetahs found on that part of the Seregeti in the African nation, Tanzania.
"If the cubs are genetically more variable it may allow them to adapt and evolve to different circumstances," Dada…
razib | May 29, 2007A few weeks ago I posted on how population bottlenecks can convert dominance variance into additive genetic variance. This is important because it is additive genetic variance that is relevant for population level directional selection upon quantitative characters. Now agnostic posts on how epistatic variance can be converted into to additive genetic variance.
razib | May 29, 2007Note: The authors have a website which summarizes their research (via Language Log).
Speaking in tones? Blame it on your genes:
People who carry particular variants of two genes involved in brain development tend to speak nontonal languages such as English, while those with a different genetic profile are more likely to speak tonal languages such as Chinese.
In tonal languages, which are most common in South East Asia and sub-Saharan Africa, subtle differences in pitch can change the meaning of vowels, consonants and syllables. Nontonal languages, which prevail in Europe, the Middle East and…
razib | May 28, 2007Kambiz @ Anthropology.net has an excellent review of the case of the Chinese warlord with "European" ancestry.
grrlscientist | May 27, 2007tags: nonfat dairy cow, marge
To meet the demands of the health-conscious consumer, how about developing cows that produce skim milk? Well, scientists have identified a cow that does this, and they hope to establish herds of the animals to meet the increased health demands from the public. The cows, which carry a particular genetic mutation, were bred from a single female, named Marge, who was discovered by researchers when they screened milk from millions of cattle in New Zealand.
"Marge looks like an ordinary Friesian cow but has three key differences. She produces a normal level of protein…
clock | May 26, 2007Larry just won the Triple Crown (or a trifecta, betting on the Triple Crown) with the third post in a trio of posts on a very important topic:
Facts and Myths Concerning the Historical Estimates of the Number of Genes in the Human Genome
The Deflated Ego Problem
SCIENCE Questions: Why Do Humans Have So Few Genes?
Alex Palazzo, madhadron, Ricardo Azevedo and PZ Myers add thoughtful commentary as well.
Of course, this is something that has been debated and studied (yes, in the laboratory) for a long time by people like Dan McShea so the issue is not going to be solved any time soon with a few…