That you probably won’t hear about on the evening news.
The Chelyabinsk meteor wasn’t as uncommon as we may think. In a rather frightening study, 33 authors, led by Peter Brown have estimated that the likelihood of a major impact is up to ten times more likely than we think.
He admits that the estimate may be high and three times more likely is probably more in line with other work on the subject. Still, that moves a multimegaton impact (like the Tunguska event) from once every couple of thousand years to once every couple of hundred years.
I wouldn’t worry. This doesn’t mean that the events of “Deep Impact” or “Armageddon” are in any way realistic.
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In yet another nail in the coffin of anti-GMO hysteria, researchers in Poland have determined that (shockingly), organisms treat GM food exactly the same as non-GM food. I’ll just quote from the abstract:
Genetically modified DNA from MON810 maize and RR soybean is digested in the same way as plant DNA, with no probability of its transfer to animal tissues or gut bacterial flora.
I’m trying to get a copy of this paper to review. I’ll add it to my ‘to-do’ list… which is getting quite long.
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Finally, in a coincidence that I would claim is karma if I believed in such a thing, Science yesterday published three papers about genetics. This summary is pretty good and I haven’t had a chance to get into the papers yet, so I’ll just leave the link here.
By what means do most DNA variants alter cellular behavior and contribute to differences in specific traits, such as height? A trio of papers in this issue by Kasowski et al. on page 750 (1), Kilpinen et al. on page 744(2), and McVicker et al. on page 747 (3) provide a framework for exploring the mechanistic link between genetic and trait variation in the human population. Specifically, they find that DNA variants influence a layer of gene regulation called epigenetics through the sequence-specific activity of transcription factors.
Those are the three papers. What they all show is that variations in DNA not only affect the proteins that the DNA codes for (and or the regulation of those protein producing genes), but that the DNA directly affects the structure that holds the chromatin together. Chromatin is a unit of DNA (146 base pairs) that is wrapped around a structure called a histone.
Changes to the histone caused by changes in DNA affect how other DNA is transcribed (the amount, the speed, or whether it is at all). In the words of the uthor
Differential transcription factor binding leads to variable histone tail modifications that collectively influence gene expression. Gene expression variations can manifest as trait differences.
For example, in the olden days (high school biology) we used to think that there was a ‘tall gene’ and a recessive ‘short gene’ for people’s height. This work shows that there really isn’t. People produce hormones that cause bones to lengthen and muscles to stretch during development and growth.
The authors here are saying that everyone produces these hormones (almost everyone) and it’s the AMOUNT of hormone that determines how tall you finally get. Epigenetic factors and genetic mutations can affect your height WITHOUT affecting the gene that produces hormones that control growth and development.
And that is how (at least one mechanism) we have a great variety in everything from height, to hair color, to skin color.
This also points out a very, very important lesson. Scientists don’t just say “evolution did it” and write book. They keep looking, they keep doing more and more science to learn more and more about how everything works.
These papers open up many more new questions than they raise and scientists will begin working on them… maybe even they started today after reading these articles.
It’s a fundamental difference between science and anti-science (like creationism).
