ScienceDaily (Sep. 3, 2009) — Scientists at the Gladstone Institute of Cardiovascular Disease (GICD) have traced the evolution of the four-chambered human heart to a common genetic factor linked to the development of hearts in turtles and other reptiles.
The research, published in the September 3 issue of the journal Nature, shows how a specific protein that turns on genes is involved in heart formation in turtles, lizards and humans.
“This is the first genetic link to the evolution of two, rather than one, pumping chamber in the heart, which is a key event in the evolution of becoming warm-blooded,” said Gladstone investigator Benoit Bruneau, PhD, who led the study. “The gene involved, Tbx5, is also implicated in human congenital heart disease, so our results also bring insight into human disease.”
From an evolutionary standpoint, the reptiles occupy a critical point in heart evolution.
That’s damn interesting! (Although I already knew it before.)
| — | Greg Laden |
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In 1952, Stanley Miller filled two flasks with chemicals assumed to be present on the primitive Earth, connected the flasks with rubber tubes and introduced some electrical sparks as a stand-in for lightning. The now famous experiment showed what amino acids, the building blocks of proteins, could easily be generated from this primordial stew. But despite that seminal experiment, neither he nor others were able to take the next step: that of showing how life’s code could come from such humble beginnings.
By working with the simplest amino acids and elementary RNAs, physicists led by Rockefeller University’s Albert J. Libchaber, head of the Laboratory of Experimental Condensed Matter Physics, have now generated the first theoretical model that shows how a coded genetic system can emerge from an ancestral broth of simple molecules. “All these molecules have different properties and these properties define their interactions,” says first author Jean Lehmann, a postdoctoral fellow in the lab, whose work appears in the June issue of PLoS One. “What are the constraints that allow these molecules to self-organize into a code? We can play with that.”
Irreducibly Complex Edition
This is a BloggingHeads video with John McWhorter and Michael Behe. It goes into evolution and genetics.
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Background
Many models used in theoretical ecology, or mathematical epidemiology are stochastic, and may also be spatially-explicit. Techniques from quantum field theory have been used before in reaction-diffusion systems, principally to investigate their critical behavior. Here we argue that they make many calculations easier and are a possible starting point for new approximations.
Methodology
We review the many-body field formalism for Markov processes and illustrate how to apply it to a ‘Brownian bug’ population model, and to an epidemic model. We show how the master equation and the moment hierarchy can both be written in particularly compact forms. The introduction of functional methods allows the systematic computation of the effective action, which gives the dynamics of mean quantities. We obtain the 1-loop approximation to the effective action for general (space-) translation invariant systems, and thus approximations to the non-equilibrium dynamics of the mean fields.
Conclusions
The master equations for spatial stochastic systems normally take a neater form in the many-body field formalism. One can write down the dynamics for generating functional of physically-relevant moments, equivalent to the whole moment hierarchy. The 1-loop dynamics of the mean fields are the same as those of a particular moment-closure.
(via cromagnon)
Here’s the abstract…
Animal species come in many shapes and sizes, as do the individuals and populations that make up each species. To us, humans might seem to show particularly high levels of morphological variation, but perhaps this perception is simply based on enhanced recognition of individual conspecifics relative to individual heterospecifics. We here more objectively ask how humans compare to other animals in terms of body size variation. We quantitatively compare levels of variation in body length (height) and mass within and among 99 human populations and 848 animal populations (210 species). We find that humans show low levels of within-population body height variation in comparison to body length variation in other animals. Humans do not, however, show distinctive levels of within-population body mass variation, nor of among-population body height or mass variation. These results are consistent with the idea that natural and sexual selection have reduced human height variation within populations, while maintaining it among populations. We therefore hypothesize that humans have evolved on a rugged adaptive landscape with strong selection for body height optima that differ among locations.
(via cromagnon)
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Fish and some amphibians possess a unique sensory capability in the so-called lateral-line system. It allows them, in effect, to “touch” objects in their surroundings without direct physical contact or to “see” in the dark. Professor Leo van Hermmen and his team in the physics department of the Technische Universitaet Muenchen are exploring the fundamental basis for this sensory system. What they discover might one day, through biomimetic engineering, better equip robots to orient themselves in their environments.
[…]
Even in murky waters hardly penetrated by light, pike and pickerel can feel out their prey before making contact. The blind Mexican cave fish can perceive structures in its surroundings and can effortlessly avoid obstacles. Catfish on the hunt follow invisible tracks that lead directly to their prey. The organ that makes this possible is the lateral-line system, which registers changes in currents and even smaller disturbances, providing backup support for the sense of sight particularly in dark or muddy waters.
This remote sensing system, at first glance mysterious, rests on measurement of the pressure distribution and velocity field in the surrounding water. The lateral-line organs responsible for this are aligned along the left and right sides of the fish’s body and also surround the eyes and mouth. They consist of gelatinous, flexible, flag-like units about a tenth of a millimeter long. These so-called neuromasts – which sit either directly on the animal’s skin or just underneath, in channels that water can permeate through pores – are sensitive to the slightest motion of the water. Coupled to them are hair cells similar to the acoustic pressure sensors in the human inner ear. Nerves deliver signals from the hair cells for processing in the brain, which localizes and identifies possible sources of the changes detected in the water’s motion.
As Jason Malloy puts it….
Overcoming bacterial defences allows the genome of one bacteria to be transplanted into another species – creation of synthetic life possible ‘in a month’, claims genome pioneer
(H/T Jason Malloy)
Microsoft filed a patent two years ago for widely used methods for determining evolutionary relatedness, causing disbelief and apprehension among researchers.
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Humans might not be walking the face of the Earth were it not for the ancient fusing of two prokaryotes — tiny life forms that do not have a cellular nucleus. UCLA molecular biologist James A. Lake reports important new insights about prokaryotes and the evolution of life in the Aug. 20 advance online edition of the journal Nature. Endosymbiosis refers to a cell living within another cell. If the cells live together long enough, they will exchange genes; they merge but often keep their own cell membranes and sometimes their own genomes.
Lake has discovered the first exclusively prokaryote endosymbiosis. All other known endosymbioses have involved a eukaryote — a cell that contains a nucleus. Eukaryotes are found in all multicellular forms of life, including humans, animals and plants.
“This relationship resulted in a totally different type of life on Earth,” said Lake, a UCLA distinguished professor of molecular, cell and developmental biology and of human genetics. “We thought eukaryotes always needed to be present to do it, but we were wrong.”
In the Nature paper, Lake reports that two groups of prokaryotes — actinobacteria and clostridia — came together and produced “double-membrane” prokaryotes.
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Researchers at Uppsala University have found that the protein coding parts of a gene are packed in special nucleosomes. The same type of packaging is found in the roundworm C elegans, which is a primeval relative of humans. The mechanism can thereby be traced back a billion years in time, according to the study presented in the journal Genome Research. Human genes are packed in nucleosomes, which contain epigenetic signals directing how the genes are to be used. The cell nucleus contains DNA, which is wound around proteins to form units called nucleosomes, not unlike pearls on a string. Genes on average contain ten protein coding units called exons. Previously there was no known correlation between nucleosomes and exons . New results show that nucleosomes are placed over exons. This means that the area containing the protein code is packed in discrete units. These results are presented by a research team at Uppsala University, led by Professor Claes Wadelius at the Department of Genetics and Pathology and Professor Jan Komorowski at the Linnaeus Centre for Bioinformatics as well as University of Warsaw.
Epigenetics is a cellular memory which identifies a cell’s identity and way to respond to the environment. Epigenetic signals control genes in a flexible manner. Each genetic package, or pearl on the string, has an epigenetic signal indicating how active it is. In the present study it was shown that there is a previously undiscovered epigenetic mark on protein coding parts of the gene.
“A gene can be read in several ways and create different proteins. We have now demonstrated that there is an epigenetic control that determines which parts of the gene that are read,” says Claes Wadelius.
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NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA’s Stardust spacecraft. “Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Dr. Jamie Elsila of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.”
[…]
“The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare,” said Dr. Carl Pilcher, Director of the NASA Astrobiology Institute which co-funded the research.
