May 1st, 2006

homuncul

БИОЛОГИЯ

из старых сообщений: кто рулит генами


"For many years, DNA and proteins have been viewed as the real movers and shakers in genomic studies, with RNA seen as little more than a messenger that shuttles information between the two. But researchers from Whitehead Institute for Biomedical Research and Massachusetts Institute of Technology have discovered that small RNA molecules called microRNAs regulate thousands of human genes--more than one third of the genome's protein-coding regions. In other words, a class of molecule once relegated to the sidelines may be one of the principal players in regulating cellular mechanisms." - jan 2005

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"There is a theory... that DNA does not function in isolation. Rather, its' function can be dictated by this modification of histones, which can determine whether DNA is exposed and accessible or not. This takes us one step closer to understanding how chemical information carried on histones, rather than DNA, is recognized and read during the regulation of genes." - jan 2005

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"The Human Genome Project has given us the genetic blueprint - the number and location of genes - but gives us very little about which genes are expressed when in different tissues and different cell types."
The researchers found that methylation patterns differed significantly when the same genes were analysed from different tissues, such as muscle and liver
In most cases, roughly 50 per cent of the reason for a disease can be ascribed to a person's genes. The other half is linked to non-genetic factors. "We believe epigenetic factors contribute a good proportion of that." DNA methylation patterns are tissue specific, says Beck. - oct 2003
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homuncul

NEUROSCIENCE

mirror neurons: популярно о зеркальных нейронах


.....When a monkey watches a researcher bring an object-an ice cream cone, for example- to his mouth, the same brain neurons fire as when the monkey brings a peanut to its own mouth.
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But if the findings, published in 1996, surprised most scientists, recent research has left them flabbergasted. Humans, it turns out, have mirror neurons that are far smarter, more flexible and more highly evolved than any of those found in monkeys
The human brain has multiple mirror neuron systems that specialize in carrying out and understanding not just the actions of others but their intentions, the social meaning of their behavior and their emotions.
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Studies show that some mirror neurons fire when a person reaches for a glass or watches someone else reach for a glass; others fire when the person puts the glass down and still others fire when the person reaches for a toothbrush and so on. They respond when someone kicks a ball, sees a ball being kicked, hears a ball being kicked and says or hears the word "kick."

"When you see me perform an action - such as picking up a baseball - you automatically simulate the action in your own brain," said Dr. Marco Iacoboni, a neuroscientist at the University of California, Los Angeles, who studies mirror neurons. "Circuits in your brain, which we do not yet entirely understand, inhibit you from moving while you simulate," he said. "But you understand my action because you have in your brain a template for that action based on your own movements.

NY Times: Cells That Read Minds (Jan 2006)
homuncul

ЭВОЛЮЦИЯ

возможно, эволюция сопровождалась неоднократными переключениями между разными вариантами генетического кода..


In a new study published online this week in the open-access journal PLoS Biology, Federico Abascal, Rafael Zardoya, and colleagues show that in the mitochondria of arthropod there are two nonstandard codes, and suggest that genetic code changes within a lineage may be more frequent than was earlier believed.

The authors aligned the mitochondrial coding sequence from >600 animal species looking for conserved codons and identifying which amino acid (AA) it specified in the corresponding protein. The most frequent AA was taken to be the canonical translation of that codon. What they found was that although most codons adhered to the common genetic code in all species, there was nonetheless a surprising trend in the arthropods, the largest of all animal phyla....

The observed variety suggests the code has changed multiple times between the two genetic codes....This might also suggest the existence of multiple other nonstandard codes within other lineages.

Genetics News


Original paper: Parallel evolution of the genetic code in arthropod mitochondrial genomes. PLoS Biol 4(5) (2006) html , pdf

PLoS Synopsis: For Arthropod Mitochondria, Variety in the Genetic Code Is Standard