Posted on 11/16/2005 3:40:35 AM PST by snarks_when_bored
* 14:02 15 November 2005
* NewScientist.com news service
* Gaia Vince
A new microscope sensitive enough to track the real-time motion of a single protein, right down to the scale of its individual atoms, has revealed how genes are copied from DNA – a process essential to life.
The novel device allows users to achieve the highest-resolution measurements ever, equivalent to the diameter of a single hydrogen atom, says Steven Block, who designed it with colleagues at Stanford University in California.
Block was able to use the microscope to track a molecule of DNA from an E.coli bacterium, settling a long-standing scientific debate about the precise method in which genetic material is copied for use.
The molecular double-helix of DNA resembles a twisted ladder consisting of two strands connected by “rungs” called bases. The bases, which are known by the abbreviations A, T, G and C, encode genetic information, and the sequence in which they appear “spell out” different genes.
Every time a new protein is made, the genetic information for that protein must first be transcribed from its DNA blueprint. The transcriber, an enzyme called RNA polymerase (RNAP), latches on to the DNA ladder and pulls a small section apart lengthwise. As it works its way down the section of DNA, RNAP copies the sequence of bases and builds a complementary strand of RNA – the first step in a new protein.
“For years, people have known that RNA is made up one base at a time,” Block 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.
Light and helium
In order to settle the question, the researchers designed equipment that was able to very accurately monitor the movements of a single DNA molecule.
Block chemically bonded one end of the DNA length to a glass bead. The bead was just 1 micrometre across, a thousand times the length of the DNA molecule and, crucially, a billion times its volume. He then bonded the RNAP enzyme to another bead. Both beads were placed in a watery substrate on a microscope slide.
Using mirrors, he then focused two infrared laser beams down onto each bead. Because the glass bead was in water, there was a refractive (optical density) difference between the glass and water, which caused the laser to bend and focus the light so that Block knew exactly where each bead was.
But in dealing with such small objects, he could not afford any of the normal wobbles in the light that occur when the photons have to pass through different densities of air at differing temperatures. So, he encased the whole microscope in a box containing helium. Helium has a very low refractive index so, even if temperature fluctuations occurred, the effect would be too small to matter.
One by one
The group then manipulated one of the glass beads until the RNAP latched on to a rung on the DNA molecule. As the enzyme moved along the bases, it tugged the glass bead it was bonded too, moving the two beads toward each together. The RNAP jerked along the DNA, pausing between jerks to churn out RNA transcribed bases. It was by precisely measuring the lengths of the jerks that Block determined how many bases it transcribed each time.
“The RNAP climbs the DNA ladder one base pair at a time – that is probably the right answer,” he says.
“It’s a very neat system – amazing to be able see molecular details and work out how DNA is transcribed for the first time,” said Justin Molloy, who has pioneered similar work at the National Institute for Medical Research, London. “It’s pretty incredible. You would never have believed it could be possible 10 years ago.”
Journal reference: Nature (DOI: 10.1038/nature04268)
agreed
No, the question is: is there anyone so irrational that they see in modern science an affirmation of their pathetic belief in 4,000 year old goat herders' myths? And by your response, the answer is: Yes.
Your copycat attempt to discredit and make me look absurd failed. Try again.
Actually, your adherence to Bronze Age fairy tales, and treating the Genesis myth as scientific fact discredits you and makes you look absurd.
I thought it was fine. I think it was blunt and truthful. This was an astonishing feat.
Proud to wear my "absurd" belief in God and creation as a badge of honor. One day, you will believe in God.
And, according to the Islamofascists, one day Allah will send you to hell. Everybody's got their stories...
Forgive? Yes.
Forget? Not a chance, especially when the error is potential future ammunition.
Is that the Christian way, or do you doubt the sincerity of snarks_when_bored's apology?
actually that contradicts the definition of faith IMO faith is a belief without knowledge:
faith (fth) KEY
NOUN:
Belief that does not rest on logical proof or material evidence. See Synonyms at belief, trust.
Not me! I think biological chemistry in action!
LOL
I made the mistake of reading and responding to that post after 3 hours of sleep and before ingestion of sufficient caffeine. My resultant stupidity lead me to believe IDists couldn't claim polymerase actions as being designed therefore assumed they would be forced to admit their religious basis.
At this rate I will give myself a headache well before lunch.
Because science and its method cannot answer "why?" questions. "Why" implies implies intention, such as that of an intelligent designer or a god, and science is not capable of answering such questions. If you were a scientist, you would have known this. It's common knowledge among scientists.
BTTT
This is not written correctly at all.
You really don't know what DNA, RNA or a polymerase are, do you?
Absolutely fantastic. I never though I'd see such a thing in my lifetime.
"Why" does not always imply intention. It may simply be a way of asking about causes, which science does all the time. Furthermore, to state point blank that science cannot address matters of "intention" is perhaps your opinion, but little more than that.
Could you please write it correctly?
Crap.
You really don't know what DNA, RNA or a polymerase are, do you?"
I think I made this point a little while ago, but don't beat him up too much on this, he apologized too :-)
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