High-mass star-forming regions

Spitzer Captures Cosmic Mountains of Creation

The largest of the pillars observed by Spitzer entombs hundreds of never-before-seen embryonic stars, and the second largest contains dozens.

"We believe that the star clusters lighting up the tips of the pillars are essentially the offspring of the region's single, massive star," said Dr. Lori Allen, lead investigator of the new observations, from the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "It appears that radiation and winds from the massive star triggered new stars to form."

Click to view 800×595 image

Tags: star birth

Formation of massive stars

As discussed before, there are two models of the star formation process: accretion and gravitational collapse. Computer modeling pointed toward the second possibility as more likely. Now there is additional evidence of this, at least in the case of massive stars.

How do massive stars form?

The locations of all the structures that were picked out at various wavelengths agree very well with the predictions of the collect and collapse process. The conclusions drawn by the team largely rely on the morphological relations between these structures. The combined picture of RCW 79 they obtained is therefore a straightforward illustration of the triggered massive-star formation process that now occurs in this region. These observations show that the collect and collapse process is the main triggering agent of massive star formation observed on the borders of this region.

Tags: star formation

Young Stars Sculpt Gas with Powerful Outflows

Young Stars Sculpt Gas with Powerful Outflows (11/10/05)

This image of star cluster NGC 346 and its surrounding star-formation region was taken in July 2004 with the Advanced Camera for Surveys aboard NASA's Hubble Space Telescope. Located 210,000 light-years away in the Small Magellanic Cloud (SMC), a satellite galaxy of our Milky Way, the cluster is one of the most dynamic and intricately detailed star-forming regions in space. A dramatic structure of arched, ragged filaments with a distinct ridge encircles the cluster.

NGC 346 - Click to view 685×800 image

Tags: star birth

Watching DNA transcription

DNA is a really long molecule -- almost arbitrarily long, in fact. A single strand of human DNA can be as long as 5 cm. But it's also very narrow, about 2 nm (2×10^-7 cm). Further, the distance between each base pair that makes up the molecule is only .34 nm. It's hard to imagine actually being able to see directly what's going on as DNA is transcribed into RNA in the first step of the process which eventually makes a protein molecule.

But that is exactly what has recently been accomplished, and it answers an obvious question: Does the RNA polymerase enzyme which transcribes DNA into RNA work by translating a single base unit at a time, or does it operate in batches of several base units? It seems that we now have the answer:

Ultra-sensitive microscope reveals DNA processes

“For years, people have known that RNA is made up one base at a time,” Block [researcher who co-designed the experimental equipment] says. “But that has left open the question of whether the RNAP enzyme actually climbs up the DNA ladder one rung at a time, or does it move instead in chunks – for example, does it add three bases, then jump along and add another three bases.

And the answer is?

“The RNAP climbs the DNA ladder one base pair at a time – that is probably the right answer,” he says.

Tags: DNA

Record ice core reveals Earth's ancient atmosphere

There are several important points in these recent results:

Record ice core reveals Earth's ancient atmosphere

The longest ice-core record of climate history ever obtained has hugely extended the detailed history of Earth's atmosphere, and shows that levels of greenhouse gases really do march in lockstep with changes in temperature.

The frozen record of the Earth's atmosphere is 3270 metres long and covers the last 650,000 years – 50% longer than before. It was obtained from the tiny air bubbles trapped in a deep ice core from Antarctica.

The tight coupling between temperatures and the greenhouse gas levels revealed by the core matches the predictions from climate models used to forecast future global warming. It also bears some good news: the warm interglacial periods between ice ages can last a long time, contrary to the view that we may already be due for the onset of the next ice age.

First point: Levels of greenhouse gases and changes in temperature are correlated.

Second point: There's a lot of variability in ice age cycles. The lengths of colder and warmer periods vary over a wide range.

...during all that time, the atmosphere has never had anywhere near the levels of greenhouse gases seen today.

Today's level of 380 parts per million of carbon dioxide is 27% above its previous peaks of about 300 ppm, according to the team led by Thomas Stocker of the University of Bern in Switzerland.

Third point: We're in uncharted territory. There is no record of any time in the last 650,000 years when the Earth's atmosphere has had the levels of greenhouse gases that it does now. Where we go from here is impossible to predict from this data... but the trend is anything but encouraging.

On the other hand, 650,000 years is just an eyeblink in Earth's history -- about .014% to be more exact.

There is further reporting on this research, and a vigorous debate in the comments about its meaning, in this article at Real Climate: 650,000 years of greenhouse gas concentrations.

The most contentions issue is with respect to the correlation of temperatures and greenhouse gas (GHG) concentrations. It appears that changes in temperature precede rather than follow GHG by perhaps 600 years. However, this lag can be explained as the result of higher temperatures (from other causes, such as variations in Earth's orbit) causing the release of GHGs from the oceans, leading to a positive feedback loop as the GHGs drive a greenhouse effect.

This discussion shows the complexity of the situation. A number of different feedback loops need to be incorporated in climate models. When done carefully, the resulting models accurately represent the historical climate record.

Tags: greenhouse gases

Cosmic Portrait of a Perturbed Family

Cosmic Portrait of a Perturbed Family

Robert's Quartet is a family of four very different galaxies, located at a distance of about 160 million light-years, close to the centre of the southern constellation of the Phoenix. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the 1830s. NGC 87 (upper right) is an irregular galaxy similar to the satellites of our Milky Way, the Magellanic Clouds. NGC 88 (centre) is a spiral galaxy with an external diffuse envelope, most probably composed of gas. NGC 89 (lower middle) is another spiral galaxy with two large spiral arms. The largest member of the system, NGC 92 (left), is a spiral Sa galaxy with an unusual appearance. One of its arms, about 100,000 light-years long, has been distorted by interactions and contains a large quantity of dust.

Click for 1280×1024 image

The Great Galactic Black Widow

The Great Galactic Black Widow (10/31/05)

In the Spitzer image, captured by a team led by University of Wisconsin-Madison astronomer Edward Churchwell, the two opposing bubbles that make up the black widow's body are being formed in opposite directions by the powerful outflows from massive groups of forming stars. The baby stars can be seen inside the widow's "stomach" where the two bubbles meet.

When individual stars form from molecular clouds of gas and dust they produce intense radiation and very strong particle winds. Both the radiation and the stellar winds blow the dust outward from the star creating a cavity or, bubble. In the case of the Black Widow Nebula, astronomers suspect that a large cloud of gas and dust condensed to create multiple clusters of massive star formation. The combined winds from these large stars probably blew out bubbles into the direction of least resistance, forming a double-bubble.

Black Widow Nebula - Click for 640×640 image


Another article: here

Tags: star birth

Large Binocular Telescope - first light

Large Binoccular Telescope Successfully Achieves First Light

The LBT's first light images were taken on 12 October 2005. The target was an edge-on spiral galaxy (type Sb) in the constellation of Andromeda known as NGC891. This galaxy lies at a distance of 24 million light years. NGC891 is of particular interest because the galaxy-wide burst of star formation inferred from X-ray emission is stirring up the gas and dust in its disk, resulting in filaments of obscuring dust extending vertically for hundreds of light-years.

The images were captured through a state-of-the-art camera known as the Large Binocular Camera (LBC), which is mounted high above the primary mirror at the telescope's prime focus. Designed by the Italian partners in the project, the LBC acts like a superb digital camera. Its large array of CCD detectors is fed by a sophisticated six-lens optical system. Scientists can obtain very deep images over a large field of view, which is important since the processes of star formation and faint galaxy evolution can be observed with unmatched efficiency.

NGC 891 - Click for 1280×1024 image


References:

Description of the First Light images from LBT
Large Binary Telescope Observatory
Another press release: here

Chaotic star birth

Chaotic Star Birth

Located 1,000 light-years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born. Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed. With NASA's Spitzer Space Telescope, scientists can detect the infrared light from these objects. This allows a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives.

NGC 1333 –Click for 720×900 image

Tags: star birth

HPV vaccine revisited

We wrote about it here: Human papilloma virus vaccine.

You know, the good news on October 6 about how one of several HPV vaccines now under development proved 100% effective at preventing cervical cancer and precancerous lesions. We also referenced a report from last April that some fundie Christians like the Family Research Council were gearing up to oppose use of this vaccine, because, just like the original birth control pill over 40 years ago, anything that can reduce the risks of having sex is bound to play havoc with the fundies' abstinence agenda.

Well very soon after our last report, this controversy was back in the news, with a vengeance.

First we have a straight, factual story about what this vaccine means to both women and men:

Cervical cancer vaccine (October 20, 2005)

Genital warts are caused by a virus called Human Papilloma Virus, or HPV. HPV is passed from person to person through sex and comes in many different forms, some of which cause genital warts, some of which have no noticeable symptoms at all. Almost 80 per cent of the adult population – whether they notice it or not – will at some point in their lives be infected with this virus.

Well, so what? Here's what:

But then in the 80’s a German scientist discovered that this common and seemingly insignificant virus causes cervical cancer.

Worldwide, cervical cancer is the second most common cancer in women, behind breast cancer. It’s most common in 30 to 50 year old women and nearly half a million women worldwide developed cervical cancer in 2002. Each year in Australia, about 740 new cases of cervical cancer are diagnosed and around 270 women die from it.

Now we know that not only does HPV cause cervical cancer, it’s the sole cause. In a study published in 1999, researchers found traces of HPV DNA in 99.7 per cent of the cervical cancer cases they looked at.

That was the bad news. But here's the good news:

Some time in 2006 we should see a new vaccine enter the market. Recent trials have shown that this vaccine, designed to protect against the two main cancer-causing forms of HPV (HPV-16 and HPV-18), prevents persistent infection by the virus in 100 per cent of the vaccinated women, and reduces cervical abnormalities by 90 per cent.

The promise of this vaccine will be to demote cervical cancer from a major to a very minor cancer. Researchers hope that it will reduce rates of cervical cancer in women across the world by 70 per cent and save around 200,000 lives every year.

Wonderful, no? Something that could, every year, save the lives of 200,000 young people who would, except for cervical cancer caused by HPV, mostly be healthy adults. Of course, there are a few legitimate questions:

Cervical cancer vaccine raises questions (October 26, 2005)

Some people are also concerned about whether existing cervical cancer screening programs will suffer, if vaccinating against some HPV strains will lead to other strains "taking over" and how to convince parents that vaccinating their children against sexually transmitted infections (STIs) is a good idea.

Fair enough. That's a legitimate scientific concern. But remember the Christian fundies, who were already on this case, as mentioned earlier? Well guess what, they're still on the case:

Cervical Cancer Vaccine Gets Injected With a Social Issue (October 31, 2005)

A new vaccine that protects against cervical cancer has set up a clash between health advocates who want to use the shots aggressively to prevent thousands of malignancies and social conservatives who say immunizing teenagers could encourage sexual activity.

And not only that, but the Bush administration has slotted the fundies into positions of governmental power:

The jockeying reflects the growing influence that social conservatives, who had long felt overlooked by Washington, have gained on a broad spectrum of policy issues under the Bush administration. In this case, a former member of the conservative group Focus on the Family serves on the federal panel that is playing a pivotal role in deciding how the vaccine is used.

"What the Bush administration has done has taken this coterie of people and put them into very influential positions in Washington," said James A. Morone Jr., a professor of political science at Brown University. "And it's having an effect in debates like this."

Some reader reaction to this article makes additional good points:

Moral Choices in a Cancer Vaccine (November 3, 2005)

The concerns about vaccination voiced by the Christian Medical and Dental Associations and the Family Research Council reveal a "better dead than red" mentality by which these organizations place their "values" above the lives of millions of women.

To put it even more bluntly, these conservative organizations prefer that women should die, rather than have the opportunity of safer sex. So much for their propaganda about a "culture of life". Another commentator, Cenk Uygur, says it well:

Why the Christian Right Doesn't Want to Fight Cervical Cancer (November 5, 2005)

But this isn’t just about controlling our sex lives anymore. This is a matter of life and death. Now they’ve gone way past acceptable. Letting over 3,000 women die of cervical cancer each year because you think it might lead to promiscuity and pre-marital sex? This is the point where your religious fanaticism ceases to be anachronistically amusing and becomes downright dangerous.

Stay tuned. There's more to this story. Much more.

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Tags: human papilloma virus

Is US becoming hostile to science?

It's certainly a reasonable question to ask:

Is US becoming hostile to science?

By Alan Elsner

WASHINGTON (Reuters) - A bitter debate about how to teach evolution in U.S. high schools is prompting a crisis of confidence among scientists, and some senior academics warn that science itself is under assault.

In the past month, the interim president of Cornell University and the dean of the Stanford University School of Medicine have both spoken on this theme, warning in dramatic terms of the long-term consequences.

"Among the most significant forces is the rising tide of anti-science sentiment that seems to have its nucleus in Washington but which extends throughout the nation," said Stanford's Philip Pizzo in a letter posted on the school Web site on October 3.

Cornell acting President Hunter Rawlings, in his "state of the university" address last week, spoke about the challenge to science represented by "intelligent design" which holds that the theory of evolution accepted by the vast majority of scientists is fatally flawed.

Rawlings said the dispute was widening political, social, religious and philosophical rifts in U.S. society. "When ideological division replaces informed exchange, dogma is the result and education suffers," he said.

And things like this are pretty alarming:

Poll: Evolution rejected by most in survey

A CBS News public opinion survey indicates most respondents do not accept the theory of evolution.

The telephone poll conducted Oct. 3-5 suggests 51 percent of those asked believe God created humans in their present form. Three in 10 believed while humans evolved, that God guided the process, and 15 percent said humans evolved independently.

Those views were similar to a November 2004 CBS poll shortly after the presidential election. In that earlier survey, 55 percent said they believed God created humans in their present form; 27 percent believed humans evolved, but God guided that process; and 13 percent said humans evolved, but God was not involved in the process.

One might reasonably entertain the hypothesis that 51% of Americans are ignorant hicks.

Or maybe it's just that large parts of the country are like Kansas:

Kansas Education Board First to Back 'Intelligent Design'

TOPEKA, Kan., Nov. 8 -- The Kansas Board of Education voted Tuesday that students will be expected to study doubts about modern Darwinian theory, a move that defied the nation's scientific establishment even as it gave voice to religious conservatives and others who question the theory of evolution.

Kan. School Board OKs Evolution Approach

TOPEKA, Kan. -- Revisiting a topic that exposed Kansas to nationwide ridicule six years ago, the state Board of Education approved science standards for public schools Tuesday that cast doubt on the theory of evolution.

The 6-4 vote was a victory for intelligent design advocates who helped draft the standards. Intelligent design holds that the universe is so complex that it must have been created by a higher power.

Critics of the new language charged that it was an attempt to inject God and creationism into public schools in violation of the separation of church and state.

"This is a sad day. We're becoming a laughingstock of not only the nation, but of the world, and I hate that," said board member Janet Waugh, a Democrat.

Of course, a blanket negative judgment of American intelligence is too harsh when there are plenty of reactions to the above news along these lines:

Created in Our Own Image

Kudos to the Kansas Board of Education ["Kansas Education Board First to Back 'Intelligent Design,' " front page, Nov. 9].

At least now I know I have a higher power to blame for poverty, weapons of mass destruction and global warming, to name a few ills in the world. It's good to know that we humans didn't "evolve" into stupidity and ignorance; we were created that way.

CHRISTINE MEIER

Springfield

(Other news stories on this: here)

But there's some grounds for hope, in that the voters of Dover, PA tossed out all of their school board which was up for re-election, though only by a small margin:

Dover school board booted out in elections

All eight Dover, Pennsylvania school board members up for re-election have been booted out after introducing intelligent design to the science classroom. In their place are a number of those who campaigned against the policy.

(Other news stories on this: here, here.)

However, according to Pat Robertson, poster boy for American religious imbecility, the whole town of Dover is gonna be sorry:

Robertson warns Pennsylvania voters of God's wrath

"I'd like to say to the good citizens of Dover: if there is a disaster in your area, don't turn to God, you just rejected Him from your city," Robertson said on his daily television show broadcast from Virginia, "The 700 Club."

"And don't wonder why He hasn't helped you when problems begin, if they begin. I'm not saying they will, but if they do, just remember, you just voted God out of your city. And if that's the case, don't ask for His help because he might not be there," he said.

But let's be charitable and assume that most Americans aren't so stupid as to believe this sort of thing. What's really the problem?

Next hypothesis: Perhaps "science" has simply fallen out of favor somehow, maybe because of religious propaganda from people like Robertson or maybe because of real failures in science itself. The evidence on the whole is against this hypothesis. It doesn't seem that science actually has fallen out of favor. Many large, expensive scientific projects -- such as the "war on cancer", the Hubble Space Telescope, and long-range programs to send humans back to the Moon and on to Mars -- still seem to have enthusiastic public support.

Furthermore, when you stop to think about it, isn't it interesting that opponents of good science, like the "intelligent design" proponents, aren't bad-mouthing science itself? (Not much, anyway, as when they disparage it as being too "materialistic".) Instead, they want their vacuous theories accepted as real science, and they'll even go so far as the Kansas state school board has attempted, to redefine science so that bogus science like "intelligent design" is admissible -- even if it means that stuff like astrology has to be accepted under the new definition too.

It's interesting, and somewhat a source of hope, that science per se has such a good image on the whole that opponents of certain parts of it (e. g. evolution) want to usurp the "trademark" (speaking metaphorically) and to promote their own unscientific nonsense as if it were valid science. Like anyone who desires to hijack a well-established trademark, such people want to take advantage of the good reputation of the proper holders of the trademark, but to substitute inferior goods for selfish advantage.

So let's try another hypothesis: Our educational system is failing, either in general or specifically with respect to science. Maybe science is just taught so badly these days that students cannot evaluate scientific information and discriminate between good science and bad science.

Now there probably really is something to that. I think there definitely is a failure in public (and most private) schools to teach science and critical thinking skills adequately. One could go into a long discussion of how science education could be improved substantially, but let's put that aside for now.

Because I also think that our schools are only partly at fault, and we can make one additional hypothesis: In our culture (as in most) there is plenty of fear of what would happen if school children and adult citizens were actually taught, in an effective way, to think critically for themselves. They might well come to doubt the lies told by the government and the proponents of an economy dependent on unwise consumption of goods by poorly educated consumers. In other words, there are powerful forces that benefit from keeping the "mushrooms" in the dark -- about many things.

In the particular case of the clamor on the part of some in favor of "intelligent design", it's not that this is something kids would naturally favor over good science on their own. There would be no resistance to teaching of evolution were it not for the unscientific alternatives being part of a package of fundamentalist religion that took root in the U. S. many decades ago and which is used by an alliance of politicians and fundamentalist religious hucksters as a tool to motivate their supporters. Again, it's a case of certain powerful groups that benefit by promoting ignorance over science.

I've mentioned this "wedge strategy" before, here, and I'll probably keep writing about it.

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Tags: creationism, intelligent design, wedge strategy

Rx: The War on Cancer

I'm recommending this article by Azra Raza from 3 Quarks Daily because it's a nice presentation of some of the problems and issues in the "war on cancer": Rx: The War on Cancer

However, one must avoid overly simplistic views of the situation. The war metaphor, to begin with, is a terrible framing of the issue. Obviously it appeals to the simple-minded American infatuation with all things militaristic, as do the other "wars" on poverty, drugs, crime, terror, and so forth. But the metaphor is badly chosen.

The Manichaean good-vs-evil framing of all those efforts is just wrong. Not that there is anything good to be said about cancer (or poverty or terror), but anthropomorphizing any of those things as if they were enemies to be "attacked" and eventually to be "defeated" is sloppy thinking. There does not exist some evil force in the universe which is tormenting unfortunate humans with these travails. So, there is nothing to "defeat". Rather, all of these things are problems to be solved.

Note that the effort to put a man on the Moon was not characterized as a war against anything, such as the wicked gravity well in which we happen to live. It was not a "war on gravity". It was simply a problem to be solved.

Solving problems takes time, not military prowess. Solving hard problems takes a lot of time. Perhaps, with respect to cancer, we are just being too impatient.

All that said, I will utilize the military metaphor anyway. As Sun Tzu wrote in the Art of War,

So it is said that if you know your enemies and know yourself, you will not be imperiled in a hundred battles; if you do not know your enemies but do know yourself, you will win one and lose one; if you do not know your enemies nor yourself, you will be imperiled in every single battle.

Thus what we need most is to understand the "enemy", cancer, better before we can "defeat" it. You might think that after all these decades and all the billions of dollars (and Yen, and Pounds, and Deutschmarks, and Euros) spent we would understand cancer thoroughly. Clearly we do not.

And it certainly isn't because everyone's scientists are venal or incompetent. (They aren't.) It's because the problem is very hard. The problem, really, is to understand in great detail how cells work, and in particular all the complexities of gene expression and regulation.

But how could we understand those at this point? We have had a relatively complete map of the human genome's nucleotides for only five years. We still don't know where all the genes are, much less what they all do, and much, much less how crucial gene programs work -- how one or several genes together trigger (or suppress) the expression of other genes in a lengthy cascade.

Cancer is ultimately a problem of gene programs gone awry due to damage in a handful of program instructions.

To "defeat" cancer, we first need to identify the failing programs. We then need to devise a strategy to neutralize the ill effects of the failing programs. And finally we need to formulate effective interventions that implement a strategy to do what we want without causing other problems.

Anyone who's ever had to debug and correct problems in an early computer, where memory is accessed through switches and flashing lights, will appreciate the difficulties.

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Update, November 10

I mistakenly failed to locate the name of the author of the article discussed above, and I apologize for that. The author is Azra Raza. Her brother Abbas kindly wrote to provide some additional information, as follows:

Though I agree that the war metaphor may be badly chosen in the case of cancer, this is a common phrase. The article by my sister that you have linked to is not at all anonymous as you say. On the contrary, her name, Azra Raza, is given right below the post, just like on every other post at 3QD. You can click on our "About Us" page for more info on any author, but since the bios there are short, I don't mind telling you that my sister Azra has been a practicing oncologist and basic scientist for more than a quarter of a century. She has more than 200 full length scientific papers to her name, and there is more about her here, if you want more.

I am, of course, aware that "war on cancer" is a very common expression. I wasn't challenging the use of the phrase in this article, but rather the very fact that it is so common -- because I think it improperly frames the issue.

Framing the issue in terms of a "war" inevitably seems to raise the wrong question. Namely, if we've been waging this "war" for almost 35 years, why haven't we "won" yet? Perhaps the misconceptions people have about America's (or science's) prowess cause them to react too strongly to the fact that this "war" hasn't yet been "won", and therefore to believe that serious mistakes have been made.

It certainly may be that there have been serious errors in judgment that various parties have made in the conduct of this "war". I'm very interested to hear anything about that which people closer to the fray can speak of. However, I still have the feeling that most people have simply underestimated the difficulty of the problem, and that with time we will solve it, more or less along the lines I suggested above.

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Tags: cancer

Is "junk DNA" really junk?

The term "junk DNA" refers to the portion of the total DNA of any organism that (as far as anyone can tell) has no identifiable purpose -- that is, DNA that isn't part of a gene which codes for a protein or some type of non-coding RNA and isn't part of a regulatory region which controls the expression of a gene.

Whatever this junk DNA may be, the interesting thing is that there seems to be a lot of it, but the amount varies widely between species. There are hints, such as the research to be discussed here, that not all of the junk DNA really has no functional purpose. So a more neutral term like "non-coding DNA" might be more appropriate.

It is estimated that about 97% of human DNA is of the non-coding sort. Other species may have much more non-coding DNA or much less, and the amount seems to have little correlation to the complexity of the organism. The single-cell Amoeba dubia may have 200 times as much DNA in its genome, while the Fugu rubripes pufferfish genome is only about one tenth as large as the human genome, yet seems to have a comparable number of genes. Most of the difference between genomes is the result of non-coding DNA. (The wide variation in genome sizes is known as the C-value enigma.)

Where could all this "excess" DNA have come from? There are various possible sources. A major source is transposons or "jumping genes", which are DNA segments that easily move around or are copied within a genome. It is estimated that transposons (in original or mutated form) make up about 45% of the human genome. Another source is viruses and retroviruses, which reproduce by inserting their genetic material (DNA or RNA) into a host genome, with the help of an integrase enzyme. If this genetic material is inserted into a germline cell, it is copied to future generations (if the host survives).

Does this non-coding DNA have any useful function or purpose, and if so, what? Various studies have suggested that there is a function, in that some parts of it seem to be more strongly conserved in evolution than can be accounted for by chance. If it really didn't have a function, then specific sequences would by mutation become different in different species, and the more distant the relationship between two species, the more dissimilarity would be expected between their non-coding DNA.

This study suggests that indeed there is more similarity than would be expected:

UCSD Study Shows 'Junk' DNA Has Evolutionary Importance

In the October 20 issue of Nature, Peter Andolfatto, an assistant professor of biology at UCSD, shows that these non-coding regions play an important role in maintaining an organism’s genetic integrity. In his study of the genes from the fruit fly Drosophila melanogaster, he discovered that these regions are strongly affected by natural selection, the evolutionary process that preferentially leads to the survival of organisms and genes best adapted to the environment. ...

Using a recently developed population genetic approach, Andolfatto showed in his study that these expansive regions of "junk" DNA—which in Drosophila accounts for about 80 percent of the fly’s total genome—are evolving more slowly than expected due to natural selection pressures on the non-protein-coding DNA to remain the same over time.

"This pattern most likely reflects resistance to the incorporation of new mutations," he says. "In fact, 40 to 70 percent of new mutations that arise in non-coding DNA fail to be incorporated by this species, which suggests that these non-protein-coding regions are not 'junk', but are somehow functionally important to the organism."

So it looks like some of the non-coding DNA probably has a function. But what? Andolfatto's study wasn't designed to answer that important question. One can guess various possibilities, such as

• A large proportion of non-coding DNA reduces the chance that harmful mutations will affect functional DNA.
  
• At the same time, slight mutations to repeated copies of functional genes may result in modified genes that improve an organism's adaptation to its environment, without losing the original gene's function while it is still needed.
  
• There may be as yet unknown regulatory functions performed by certain DNA segments, which facilitate or inhibit the expression of real genes in environmentally-dependent circumstances.
  

The investigation of non-coding DNA seems likely to keep molecular biologists busy for some time to come.

Another article on this research: Time to stop trashing junk DNA

Much more information on junk DNA: EvoWiki article

Tags: junk DNA, non-coding DNA

Can Brain Scans See Depression?

Can Brain Scans See Depression?

Not long ago, scientists predicted that these images, produced by sophisticated brain-scanning techniques, would help cut through the mystery of mental illness, revealing clear brain abnormalities and allowing doctors to better diagnose and treat a wide variety of disorders. And nearly every week, it seems, imaging researchers announce another finding, a potential key to understanding depression, attention deficit disorder, anxiety.

Yet for a variety of reasons, the hopes and claims for brain imaging in psychiatry have far outpaced the science, experts say.

After almost 30 years, researchers have not developed any standardized tool for diagnosing or treating psychiatric disorders based on imaging studies.

Several promising lines of research are under way. But imaging technology has not lived up to the hopes invested in it in the 1990's - labeled the "Decade of the Brain" by the American Psychiatric Association - when many scientists believed that brain scans would turn on the lights in what had been a locked black box.

Now, with imaging studies being published at a rate of more than 500 a year, and commercial imaging clinics opening in some parts of the country, some experts say that the technology has been oversold as a psychiatric tool. Other researchers remain optimistic, but they wonder what the data add up to, and whether it is time for the field to rethink its approach and its expectations.

Tags: brain scans

The nucleus of active galaxy NGC 1097

Feeding the Monster

Near-infrared images of the active galaxy NGC 1097, obtained with the NACO adaptive optics instrument on ESO's Very Large Telescope, disclose with unprecedented detail a complex central network of filamentary structure spiralling down to the centre of the galaxy. These observations provide astronomers with new insights on how super-massive black holes lurking inside galaxies get fed.

NGC 1097 – click for 1467×1695 image


The scenery there is beautiful, but you probably wouldn't want to live there...

Tags: active galactic nuclei, black holes