DNA, Fifty Years To the Day 202
An anonymous reader writes "Today being the fiftieth anniversary (April 2, 1953) of the Watson-Crick double-helical, DNA discovery [to quote, 'We wish to put forward a radically different structure...'], there is an interesting tally of completed gene sequences here, and ones still being worked, including the Ames strain of the anthrax bacteria. It also appears that the only lifeforms not using DNA for code storage are a few viruses like the common cold."
Re:As always, (Score:3, Insightful)
Oh, I don't know about that. Watson and crick came up with some realizations that were pretty important, even if you NEVER actually saw the molecule.
One of the realizations that they made was that there had to be a minimum of three identification units to code for each amino acid, and that more than three would be wasted. Now that sounds pretty simple, doesn't it? But even if you get to see the molecule, if you don't understand that you need to look at three sequential base pairs (a codon) together, and that you hence need to have the alignment right, then actually seeing the structure of the molecule doesn't get you very far.
For the curious, the reason that they needed a minimum of three base pairs was this:
You have four different ways to get a single base pair. If a single base pair were the functional unit, you could code for a total of four different amino acids. Way too low. With two sequential base pairs, you could code for sixteen. Still too low. If you use three sequential base pairs, you could code for up to 64 distinct amino acids, which more than covers the number of aminos that humans were known to be capable of producing.
steve
Re:Rosalind Franklin (Score:2, Insightful)
Re:Some interesting info... (Score:5, Insightful)
<QUOTE>It's interesting to note that since their discovery of DNA's double-helical structure, neither Watson nor Crick have discovered or published anything significant since then.</QUOTE>
RUBBISH. Francis Crick proposed the Central Dogma of Molecular Biology [euchromatin.org], which is at least as important as his proposed model of DNA. In a nutshell, the central dogma states that the information encoded in the linear sequence of nucleotides in genomic DNA is transcribed into the linear sequence of nucleotides in RNA, and that the linear sequence of nucleotides in RNA is translated into the linear sequence of amino acids in proteins. At the time Crick postulated this, the link between RNA and the other two was very poorly understood. This was a remarkable contribution to the field. Crick did a whole lot more than just model building.
Re:Rosalind Franklin (Score:5, Insightful)
Even if you are unwilling to recognize this fact, I hope you will not unkowingly sully the name of Crick. Watson was responsible for accquiring the unreleased image of the B form of DNA. Whether or not Watson obtained this image without Franklin's permission, Cricks was unaware. If you must demonize anyone, it should be Watson. Everything he has said in the ensuing years has shown just how pompous and deceitful he is.
But no matter how detestable Watson may be, he and Cricks were the first ones to correctly determine that DNA was helical in shape. There is no evidence to suggest otherwise.
Re:As always, (Score:4, Insightful)
Pauling did publish a proposed structure for DNA a few weeks before W&C's paper (in fact, it was his publication that drove them to have another shot at model building) - but Pauling's model was attrocious. Like W&C's first attempt, it was a triple helix with the phosphates on the inside, not on the outside (a fact which, incidentally, was demonstrated by Franklin a year before).
But, W&C or Pauling would have certainly figured it out much faster if they had access to her information.
I don't know what you're talking about here - W&C did have access to her data, without her knowledge or permission - and it was the only way they could propose a model. To put it simply, her oft-reprinted photo was the supreme evidence that the B-form of DNA was a helix.
And Rosalind Franklin (and Ray Gosling, her PhD student) were very, very close to solving the structure, not only of the B-form of DNA but also of the dehydrated A-form of the molecule. They had recognised that both forms were a double helix and had come close to recognising the significance of the the Chargraff ratios of base-pairs at the time of W&C's publication. Their only "failing" was that they wanted to make sure that any model they proposed was in fact the correct one by having X-ray crystallographic data to support it. W&C never cared about any of that, and never bothered to check whether their model was accurate. That's why they "figured it out faster"!
Re:Some interesting info... (Score:3, Insightful)
I've heard it said that it takes anywhere from 10 to 30 years for the value of a scientific advance to be realized, and this fits with my own observations. If you look at the progress of crystallography since Franklin's DNA pictures, it took decades for the field to yield more than a handful of high-resolution macromolecular structures and only in the past ten to fifteen years has it really exploded. Yet much of the fundamental chemistry and physics was established before the current leaders in the field went to college.
I'd also argue that this is why publically-funded basic research is essential, but that's another rant.
Re:not lifeforms (Score:2, Insightful)