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)
there seems to be too much emotional equity in most of the arguments here, this results in slanging matches. I had hoped for an enlightening scientific debate on this topic. so far we are going out on ID tangents
Ichneumon - "This sounds like splitting hairs."
IMHO, 'r9etb' has a valid argument here.
Kind of what the whole experiment was about. Science had a 'hunch', but no definitive evidence.. No?
From the article - “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.
Do you believe in miracles?
Did Jesus turn water into wine? Did Jesus walk upon the water? Did Jesus heal a man born blind? Did God write the 10 commandments on tablets of stone with his own hand?
Do you believe any of that stuff?
Please read my posts back to you, it seems you are repeating a separate set of off topic questions to me, why is that?
That fairly well represents your point of view, not mine.
What other logical fallacies are open to the scientist?
Any, and every, one of them. But with the proviso their use may not lend credence to his statements. Now hop on your little rocking horse and tell everyone how logical fallacies are to be encouraged in scientific inquiry.
You apparently have a problem with the notion that intelligence and design can be scientifically ascertained. Do you really think one must engage in logical fallacies, e.g. arguments from incredulity, to infer that an automobile is the product of intelligent design, and, by extension, an intelligent designer?
Must be awfully dsutned in that sbrtl;ijbELE.
What does that have to do with science?
or even the topic of dna and genetic expression?
Many evolutionists have referred to the bible stories as fables. That seems to be the general consensus among "Christian" evolutionists regarding the creation account in Genesis, the story of Noah, the Story of Jonah, etc. So my question was serious and not meant to be insulting. I just would like to get a feel for how you reconcile your evolution and your Christianity. Anyone can call himself a scientist and that does not mean that objectively they are a scientist. Likewise any atheist can call himself a Christian, but belief in God, I would think, is a prerequisite to being a Christian and IMO, belief in the God revealed in the Bible is such a prerequisite. (At least it used to be).
While that is most likely true, I don't know if it is undeniably true. Science has evolved by leaps and bounds. Who knows what is yet to be discovered.
The very idea of connecting glass beads to either end of a single DNA strand is, to me, astounding.
Is that a yes? This is important. Did God write the 10 commandments on the tablets of stone with his own hand? Do you believe that?
It is not off topic as you claimed to reject entirely the idea that the creation was intelligently designed, yet you claim (apparently) to believe in the God of the Bible. I'm trying to see how you reconcile that in your mind.
You said you are more than willing to discuss this matter further. Have you changed your mind?
What do they contain?
So basically I can derive from your comment here that you first made an assumption about ME. Took that to the next level and started to get hostile based on a preconceived view of my opinions without, giving me the courtesy of deciding what i think for myself. Is that it in a nutshell?
"So my question was serious and not meant to be insulting. I just would like to get a feel for how you reconcile your evolution and your Christianity."
try listening once in a while and maybe you will get my perspective correctly from the horse's mouth? This is just a friendly suggestion. :-)
"Anyone can call himself a scientist and that does not mean that objectively they are a scientist."
It is what I am trained to be, also my vocation. So that to me is sufficient. not sure what you mean here?
"Likewise any atheist can call himself a Christian, but belief in God, I would think, is a prerequisite to being a Christian and IMO, belief in the God revealed in the Bible is such a prerequisite. (At least it used to be)."
be careful it is for God alone to say who is and who is not a Christian. We tend as people to get that wrong usually. Case in point the religious crowd (scribes and pharisees) who where the religious establishment. And the criminal who was on the cross next to Jesus. Now according to your definition of a Christian the guy on the Cross next to Jesus was not a Christian.
I thought this was a religious discussion.
I completely answered that in post 677 did you read any of it?
I meant nothing hostile. I was simply trying to see how you reconcile your Christianity with your denial of the idea that life was intelligently designed.
It appears I have struck a nerve with you. So since it is obvious that you don't want to answer any of the questions I have posited, I will stop asking them.
Carry on.
Later utilized by Tertullian and the White Queen.
Sublime!
OK thats fine please proceed to post 677 where I presented my views and perspectives unambiguously and in crystal clarity. I look forward to hearing your informed opinions after that :-)
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