genetics

I straddle the line between being a population biologist and a molecular geneticist. That's a self-congratulatory way of saying that I am an expert in neither field. But existing in the state I do allows me to observe commonalities shared by both. For example, both fields have terminology (or what the uninitiated would call jargon) that lack sufficient definitions. Amongst my minimal postings from last week were included a couple of riffs on species and speciation (the first, the second) getting at the lack of a coherent definition of species. My conclusion is that there is not, nor will…
In the series of "Basic Concept And Terms" (yup, I know, John is well known for misspelling people's last names, including mine), several people have already chimed in with their own definitions of the "gene", demonstrating how unclear this concept is and how much disagreement there is among the practitioners depending on the type of research they are doing (e.g, molecular biology, developmental biology, population genetics, evolution, etc.). See how the term was defined and explained by PZ, Sandra and Greg so far and you'll see those differences in emphasis. Now Larry Moran joins the fray…
Hey, I'm teaching a genetics class this term, and someone is taking one. I'm going to be spending part of my day setting up flies for an upcoming lab…this looks awfully familiar.
This streaming video, below the fold, was old when I was an undergrad, but it never lost its instructive nor entertainment value in the classroom. As an added bonus, one of my biochemistry professors, who developed knockout mice, was a character in this film. More info on this film; Directed in 1971 by Robert Alan Weiss for the Department of Chemistry of Stanford University and imprinted with the "free love" aura of the period, this short film continues to be shown in biology class today. It has since spawn a series of similar funny attempts at vulgarizing protein synthesis. Narrated by Paul…
tags: cancer, p53,tumor suppressor, gene, oncology Image modified. When I was an undergrad, I worked in a lab that studied p53, a gene that acts as a tumor suppressor. At that time, it was thought that most cancers resulted from a defective form of p53 or after p53 had inadvertently been turned off because p53 controls the cycle of cell proliferation, telling the cell when it is appropriate to divide, activating the cell's DNA repair mechanisms and preventing cells with damaged DNA from dividing. At that time, it was thought that cancerous tumors could be treated and possibly cured by…
tags: Y chromosome, genetics, Britain, African A study of the human Y chromosome found that seven men with a rare Yorkshire surname carry a rare genetic signature found only in people of African origin. Researchers Turi King and Mark Jobling from Leicester University found that the men appear to have shared a common ancestor in the 18th Century, but the African DNA lineage they carry could have reached Britain centuries earlier. This discovery was the result of genetic research that analyzed the relationship between the Y chromosome and surnames. The Y chromosome is normally found only in…
Thinking about it today, I realized there is a "Basic Concept" that I think I should touch upon, and that is linkage disequilibrium (LD). Notice the wiki link? I do that whenever I mention LD because it is such an essential concept for some of the evolutionary ideas which I am interested in, but often not necessarily a transparent or clear one to the lay person. Its lack of obviousness isn't due to complexity, LD is pretty simple, rather there are particular background ideas which one needs to firmly have in mind before one can easily grasp it. For this reason I've placed an image of a…
So I near the end of my survey of chapter 5 of Evolutionary Genetics: Concepts & Case Studies.1 Today, we address environmental variation, but I think sometimes the end is the beginning, so I quote: Random environment models have many technical aspects...that make them difficult to analyze. As a result, they have ben largely ignored in population genetics. This is unfortunate as it is clear that environments do change and that adaptive evolution is driven by these changes. The last sentence made me think, "No shit sherlock." This is a pretty deep indictment of population genetics,…
A reader just informed me that Bob Trivers just won the Crafoord Prize in bioscience! For those who would like to become more familiar with Trivers' work, I highly recommend Natural Selection and Social Theory. Genes in Conflict is also a good read if you want some molecular level evolutionary exposition. Finally, Trivers looms large in both Mother Nature and Defenders of the Truth. If you don't know anyting about Trivers, I suggest this Edge Special Event. Robert Trivers introduced concepts such as reciprocal altruism in the 1970s which revolutionized social theory, and serve as the atomic…
Two science blogging carnivals have been posted in the past few days. The first edition of Oekologie (ecology and environmental science) is up at The Infinite Sphere, and Aardvarchaeology has the newest Four Stone Hearth (anthropology). Also, Evil Monkey is scheduled to post a fresh edition of Mendel's Garden any minute now -- or two days ago. Anyway, keep your eyes peeled for that one too.
I mulled over some of the suggestions in my request for basic topics to cover, and I realized that there is no such thing as a simple concept in biology. Some of the ideas required a lot of background in molecular biology, others demand understanding of the philosophy of science, and what I am interested in is teetering way out at the edge of what we know, where definitions often start to break down. Sorry, I have to give up. Seriously, though, I think that what does exist are simple treatments of complex subjects, so that is what I'm aiming for here: I talk a lot about genes, so let's just…
There are a lot of different ways for animals to determine which individuals develop into boys and which ones become girls. You're probably most familiar with the form of chromosomal sex determination that utilizes X and Y chromosomes -- males are XY and females are XX. There are others, including ZW (males are ZZ, females are ZW) and environmental sex determination (e.g., sex can be determined by egg rearing temperature). One of the most interesting sex determination systems -- from an evolutionary perspective -- involves differences in ploidy between males and females. Hymenoptera (ants,…
Jonah over at The Frontal Cortex has some commentary up on the gay sheep story. A reader pointed out that this controversy started off with some wild claims made by PETA. Nevertheless (more at Andrew Sullivan's), no matter the details of the claim, there are a few points I'd like to pick up on.... Jonah says: So here's my hypothesis: if you select against homosexuality in a biological community, you will also be selecting against our instinct for solidarity. The same genes that give rise to gayness might also give rise to cooperation. When scientists create a population of all heterosexual…
Mutations are the fuel that drives the engine of evolution. Without mutations there would be no variation upon which natural selection and other evolutionary forces could act. Furthermore, much of the theoretical results regarding evolutionary genetics depend on estimates of mutation rates. For example, Kimura showed that the rate of fixation of neutral mutations is equal to the neutral mutation rate. Additionally, many models to explain the evolution of sex and recombination depend on the amount of deleterious mutations per genome per generation (U). A group led by Peter Keightly (DOI) have…
Jason Rosenhouse and John Hawks have both commented on the introgression of cattle alleles into wild bison. J & J have hit many of the salient points, but let me suggest one issue: not all genetic loci are created equal. That is, "neutral" markers should be weighted less than "functional" markers. Of course, neutral markers probably aren't all neutral, and many functional markers are functionally relevant only in specified environmental contexts. The problem with these sort of questions is that I believe our "species concepts" are derived from gestalt psychology and our intuitive…
Over the past month or so I've been blogging chapter 5 of Evolutionary Genetics: Concepts & Case Studies. This chapter covers "stochastics processes," basically the random elements in the flux of gene frequencies in biological populations. Now, I'm a selection man for real, but to understand selection you need to put it into the context of evolutionary dynamics as a whole, and chance is essential to properly comprehending necessity. First I covered the immediate danger of extinction for a new mutant allele, even those favored positive selection's kiss. Then I traced out the…
Over in The Corner they are talking about eugenics. Of course my friend John Devilshire, I mean, Derbyshire, started it all off. 1) I think Jonah Goldberg is correct that eugenics we do will be not called eugenics, while eugenics which is ethically objectional will be thrown under that term. 2) I think that the "Great Risk Shift" combined with greater discernment powers of medical genomics will make some form of government subsidized health care in the United States pretty inevitable (the short of it is that the middle class will start to get scared and want protection, and what the middle…
Differential fitness costs of reproduction between the sexes: We found that increasing number of offspring (parity) and rates of reproduction were associated with reduced parental survivorship, and significantly more for mothers than fathers. Parental mortality resulted in reduced survival and reproduction of offspring, and the mothers' mortality was more detrimental to offspring than the fathers'. Increasing family size was associated with lower offspring survival, primarily for later-born children, indicating a tradeoff between offspring quantity versus quality. Also, we found that the…
The headline says it all: Down screening urged for all pregnant women. Related: To breed a better human - we have the technology.
Science told: hands off gay sheep: Scientists are conducting experiments to change the sexuality of "gay" sheep in a programme that critics fear could pave the way for breeding out homosexuality in humans. You can read the whole article yourself. Randall Parker has been saying for years that genetic engineering will accentuate human differences as parents will choose to invest in alternative enhancements with their finite dollars. The vectors may remain the same, but the magnitudes could increase, as religious parents breed super-religious offspring, secular parents start spawning born…