genetics
razib | June 28, 2006In Unequal by nature: A geneticist's perspective on human differences, James F. Crow states:
Two populations may have a large overlap and differ only slightly in their means. Still, the most outstanding individuals will tend to come from the population with the higher mean.
This is a trivial observation. It is biologically relevant because heritable quantitative traits are to a great extent the raw material for evolution, and, they generally follow an approximate normal distribution. The reasoning is simple, many loci of small independent additive effects are a good approximation of the…
razib | June 27, 2006In the long winded post below I referred to genetic conflicts in pregnancy. If you are curious about this, I highly recommend Mother Nature by Sarah Hrdy. Though the topic is placed in the context of female evolution (of our species) in general, it gets a thorough treatment. If you are interested in the technical literature, I recommend this review, Genetic Conflicts in Pregnancy by David Haig. Since it is a review, it is less analytical and formal than much of Haig's work, so it reads easily. You can get the pdf on Haig's website.
razib | June 27, 2006Janet points me to this post which points to this research which reinforces the theory that placental environment might have a strong effect on the phenotype of the fetus. Since I've expressed an interest in genomic imprinting let me respond to Jill at Feministing's query, "why do we have to know?", she doesn't have to, but some of us certainly follow this research closely. The reason isn't because we are obsessed with the biology of homosexuality, as that is the phenotype in question, but rather it elucidates questions and dynamics in evolutionary biology that we find interesting.
As to…
clock | June 26, 2006
In the beginning, there was period.
Before 1995, the only known circadian clock genes were period (Per) in Drosophila melanogaster (wine fly) and frequency (Frq) in Neurospora crassa (bread mold). Some mutations, though not characterized at the molecular level, were also known in Chlamydomonas, Euglena as well as the famous Tau-mutation in hamsters.
I still remember the strained mathematical models attempting to account for a 24-hour rhythm with just a single gene controlling its own expression. We now know that multiple genes are involved in circadian function in invertebrates and…
razib | June 26, 2006My 10 questions for James F. Crow are up. It isn't often that a nobody gets to interview the greatest living thinker in a field (theoretical population genetics), so you should check it out.
razib | June 22, 2006Three human gene variants appear to influence tb susceptibility:
Approximately one-third of the world's population is thought to be infected with the M. tuberculosis pathogen, yet only about 10 percent becomes ill with the active disease. Researchers suspect that a variety of factors interplay to determine who develops the full-blown disease. For example, in February 2006 Harvard School of Public Health (HSPH) researchers were part of a team that identified a mechanism that explains why people of African descent may be more vulnerable to the disease.
The paper is reputedly in the PNAS -…
evolgen | June 22, 2006
Hsien Lei will be hosting the second edition of Mendel's Garden at Genetics and Health. Submission information is available here.
razib | June 21, 2006Steve points me to this story which reports that the man reported to be the first direct line descent of Genghis Khan among Europeans is not a Khan. Nevertheless, the more important point holds: the success of the Khan patrilineage seems distinctly an Asian phenomenon, showing how fickle social status for males can be across space & time....
razib | June 20, 2006Over at The Corner at National Review Online John Derbyshire has been getting into a debate with his colleagues over Judith Rich Harris' work, and her two books The Nurture Assumption and No Two Alike. I find it amusing when scientific controversy comes crashing into the punditocracy, though I think it is also a good thing. To frame the issue properly, there is consistent evidence that the majority of non-genetic variation in personality is due to non-shared (i.e., non-home) environment. Judith Rich Harris proposes that peer groups account for this non-shared environment, though this is…
clock | June 19, 2006Pedro Beltrao, who blogs on Public Rambling is starting Bio::Blogs, a carnival of bioinformatics and computational biology.
razib | June 19, 2006A few weeks ago I was posting on genomic imprinting. I will continue that series in the near future, but until then, I point you to my 10 questions for David Haig, the theorist who originated many of the ideas which I discussed and will discuss. Though Haig is not a popularizer himself, he shows up in Matt Ridley's work, as well as Mother Nature by Sarah Hrdy and Natural Selection and Social Theory by Bob Trivers. You may read many of his papers without academic access, so I highly recommend readers to go straight to the source in this case!
razib | June 19, 2006Jake at Pure Pedantry has a lengthy post on heritability. It makes concrete (using real psychological illneses, etc.) some of my points in my previous post where I discuss the complexity of behavioral genetics.
Two issues of note. First, Jake used the example of Huntington's Disease as "100% heritable." I think this is going to confuse people. There is often a distinction between "broad sense" and "narrow sense" heritability, the latter includes dominance effects into the genetic variation component,1 while the latter is focused on additive genetic variation.2 In most genetic discourse…
pharyngula | June 18, 2006The very first edition of Mendel's Garden, a genetics carnival, is now up at The force that through….
While I'm at it, let me remind everyone that a new Tangled Bank will be appearing at Centrerion on Wednesday—now is the time to send entries to me or host@tangledbank.net.
razib | June 18, 2006This hilarious article about "confirming" your descent from Confucius is making the rounds.
Now, my understanding is that the patrilineage of Confucius remains to this day. So the people who would seek confirmation would often have a tradition of descent from the great sage himself. But, I note tradition. We all know that "ancestors" can be concocted, and, we also know that sometimes patrilineages can be "interrupted." When English geneticist Bryan Sykes tested individuals with his surname across the British Isles he found that ~50% of individuals were of the same Y chromosomal lineage.…
evolgen | June 18, 2006The first ever edition of Mendel's Garden, a blog carnival devoted to genetics, has been posted at The force that through... If you would like to contribute to the next edition, you can find information here.
clock | June 17, 2006The very first edition of Mendel's Garden, the carnival of genetics, is up on The Force That Through....
Pediatric Grand Rounds, Volume 1 Edition 5, is up on Unintelligent Design.
pharyngula | June 16, 2006
Maternal effect genes are a special class of genes that have their effect in the reproductive organs of the mutant; they are interesting because the mutant organism may appear phenotypically normal, and it is the progeny that express detectable differences, and they do so whether the progeny have inherited the mutant gene or not. That sounds a little confusing, but it really isn't that complex. I'll explain it using one canonical example of a maternal effect gene, bicoid.
Bicoid is a gene that is essential for normal axis formation in the fly, Drosophila. It is this gene product that…
razib | June 15, 2006On the heels of the asinine review of Before the Dawn in Nature, I see Carl is linking to some recent papers that are coming out in regards to positive selection in our own storied lineage. I must say that the new one in Science is quite phat in its broad sweep. Pictures below the fold....
Show me the money honey, you can sneer about incomplete evidence for selection on human lactase persistence, but saying it just ain't gonna make it so.
razib | June 15, 2006Dave and Jonah have both commented on this piece in The New York Times which is something of a mismash of recent studies coming out of the field of behavior genetics. The best thing about the piece, from my selfish angle, is that it references Contingency Table, now absorbed into my other weblog, who was riffing off one of my older posts here at Science Blogs.
The biggest problem with pieces like this isn't the genetics or psychology, it is the utter lack of focus on the importantce of probability distributions and the concept of expectation. There are several types of genetic traits. Some…