There are exactly 20 standard amino acids — complex molecules that combine to form proteins, which carry out instructions specified by RNA and DNA, its double-stranded and self-replicating descendant.
Ten were synthesized in the famous 1953 Miller-Urey experiments, which modeled conditions believed to exist in Earth’s early atmosphere and volcano-heated pools. Those 10 amino acids have also been found in meteorites, prompting debate over their role in sparking life on Earth and, perhaps, elsewhere. [Bold mine]
If the observed patterns of amino acid formation — simple acids require low levels of energy to coalesce, and complex acids need more energy — indeed follow thermodynamic laws, then the basic narrative of life’s emergence could be universal. [Bold mine]
"Thermodynamics is fundamental," said Pudritz. "It must hold through all points of the universe. If you can show there are certain frequencies that fall in a natural way like this, there is an implied universality. It has to be tested, but it seems to make a lot of sense."
Citation: "A thermodynamic basis for prebiotic amino acid synthesis and the nature of the first genetic code." By Paul G. Higgs, Ralph E.
Pudritz. arXiv, April 6, 2009.
PhysORG - New nucleotide could revolutionize epigenetics:
Anyone who studied a little genetics in high school has heard of adenine, thymine, guanine and cytosine - the A,T,G and C that make up the DNA code. But those are not the whole story. The rise of epigenetics in the past decade has drawn attention to a fifth nucleotide, 5-methylcytosine (5-mC), that sometimes replaces cytosine in the famous DNA double helix to regulate which genes are expressed. And now there's a sixth. In experiments to be published online Thursday by Science, researchers reveal an additional character in the mammalian DNA code, opening an entirely new front in epigenetic research.
The work, conducted in Nathaniel Heintz's Laboratory of Molecular Biology at The Rockefeller University, suggests that a new layer of complexity exists between our basic genetic blueprints and the creatures that grow out of them. "This is another mechanism for regulation of gene expression and nuclear structure that no one has had any insight into," says Heintz, who is also a Howard Hughes Medical Institute investigator. "The results are discrete and crystalline and clear; there is no uncertainty. I think this finding will electrify the field of epigenetics.
Genes alone cannot explain the vast differences in complexity among worms, mice, monkeys and humans, all of which have roughly the same amount of genetic material. Scientists have found that these differences arise in part from the dynamic regulation of gene expression rather than the genes themselves. Epigenetics, a relatively young and very hot field in biology, is the study of nongenetic factors that manage this regulation."
PhysORG - A secret to night vision found in DNA's unconventional 'architecture':
Researchers have discovered an important element for making night vision possible in nocturnal mammals: the DNA within the photoreceptor rod cells responsible for low light vision is packaged in a very unconventional way, according to a report in the April 17th issue of Cell, a Cell Press publication. That special DNA architecture turns the rod cell nuclei themselves into tiny light-collecting lenses, with millions of them in every nocturnal eye.
"The conventional architecture seen in almost all nuclei is invariably present in the rod cells of diurnal mammals, including primates, pigs and squirrels," said Boris Joffe of Ludwig-Maximilians University Munich. "On the other hand, the unique inverted architecture is universally present in nocturnal mammals," for instance, mice, cats and deer.
"Diurnal nuclei are basically scattering obstacles," he said. "In nocturnal animals, they are little lenses. In one case, light is scattered in all directions and in the other it is focused in the forward direction," meaning that even at night, what little light there is can travel deeper into the eye where it can be perceived.
[M]easurements of how individual nuclei taken from the rod cells of nocturnal animals interact with light show that they act as collecting lenses. Computer simulations indicate that columns of such nuclei like those found in nocturnal animals' retinas would channel light efficiently toward the light-sensing rod outer segments.
The importance of this special nuclear arrangement comes only when you consider the columns, Guck said. "If each nuclei scattered light, it would all be over. The inversion in nocturnal animals makes sure that light is passed from one nucleus to the next. It is handed down so that it doesn't scatter."
The results show that despite the strong evolutionary conservation of the conventional pattern, nuclear architecture in rod cells was modified several times in the evolution of mammals, Joffe said.
Wired Science - Viral Missing Link Caught on Film:
The virus was originally discovered infecting amoebas in a Parisian water tower in 1992. It was orders of magnitude bigger than any other virus — so large, in fact, that researchers figured it was a microbe.
Whereas the DNA of other viruses are tightly wrapped, there’s a large gap between the mimivirus genome and its capsid. In some ways, this resembles less the structure of a virus than of a living cell, in which DNA is contained in a nucleus, which in turn floats in cell-wall-enclosed cytoplasm.
“The new structural finds, along with previous genetic and morphological work, confirm that mimivirus is an odd mix of genes and parts found in viruses, bacteria and even eukaryotes, the organisms that sequester their DNA in a nucleus,” write the researchers.
Citation: “Structural Studies of the Giant Mimivirus.” By Chuan Xiao, Yurii G. Kuznetsov, Siyang Sun, Susan L. Hafenstein, Victor A. Kostyuchenko, Paul R. Chipman, Marie Suzan-Monti, Didier Raoult, Alexander McPherson, Michael G. Rossmann. PLoS Biology, April 28, 2009.
Image: PLoS Biology
From Slashdot - Human Language Gene Changes How Mice Squeak:
"Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany have engineered a mouse whose FOXP2 gene has been swapped out for a different (human) version. This is interesting because the gene is implicated in human language, and this has changed how mice squeak. 'In a region of the brain called the basal ganglia, known in people to be involved in language, the humanized mice grew nerve cells that had a more complex structure. Baby mice utter ultrasonic whistles when removed from their mothers. The humanized baby mice, when isolated, made whistles that had a slightly lower pitch, among other differences, Dr. Enard says. Dr. Enard argues that putting significant human genes into mice is the only feasible way of exploring the essential differences between people and chimps, our closest living relatives.' The academic paper was published in Cell."
