Double Helix My Arse

Speaking of things I love about Singapore...

A Double Helix is a spiral contained within another spiral, not just two two spirals running out of phase side by side together. The proposed Genetic Hub Bridge seems to have several supporting spirals running along it, but those swallows doth not a summer make for this little black duck. [Cartoon reference! I had a friend who's entire lexicon of metaphor came from Bugs Bunny.]


If it was truly to be built in the shape of Crick and Watson's double helix, the walkway itself would be spiralling as well, making it impossible to walk upon. See how the base pairs are shown in this illustration what I hastily prepared ripped off from some patented copyrighted website... [Morecombe a Wise reference: the man has depth!]


The "double" refers not to the second of the blue lines (that used to be my mistake, but I is smarter now) , but the shape of the whole thing. Think of the two blue lines and the base pairs as ONE of the helices. THEY are looping as a unit themselves, and it's that looping which makes the second or "double" helix.

Think of a spiral staircase where the inner edges of the steps don't reach the central column but have their own inner (double) spiral.

And when lain down horizonatally such a structure is unwalkable. Sort of like a Democratic Singapore.


Of course I could be mistaken.


Am I in a whingeng mood lately OR WHAT!

I feel like a rolled up carpet: I need to get laid.



Posted by: expat@large on Mar 09, 06 | 10:21 pm | Profile


lol....this lol was recorded secretly in oxley rd detention centre.

Posted by: TheOriginalTrousersnake on Mar 10, 06 | 12:51 am

I'm afraid your staircase analogy commits the very fallacy you claim to have learnded is not true.

If a double helix were like a staircase whose steps don't reach the centre, then the inner rail (your inner double spiral) is no different to your 'second blue line' syndrome.

The double helix structure is like a staircase where the steps continue through the centre of the staircase, thereby creating a double staircase on the one structure.

Imagine two people on such a staircase, one about to descend the stairs from the top, the other about to climb. If these two peple happen to enter the staircase on alternate sides of the central axis, they may both reach the end of the staircase without having even known the other was also on the stairs.
In effect there are two staircases (two helices - a double helix) sharing the same axis.

In the case of DNA (as portrayed in your diagram) the central axis is a somewhat corkscrewed itself, and there is no physical central connecting pole - just a logical one that can be considered to be at the central point of each base pair.

The bridge could probably work if it were to spin in a direction opposite to that of the bridge's persistence. Of course people using the bridge would have to be induced to walk at a constant pace...

Hey... They could make it a travellator! People could only stand in the lowest point on the travellator, and move forward across the bridge at the same pace as it rotates on its central axis.

What do we reckon guys? Is it a good idea or what?
Am I certifiable?

Posted by: rambeaux2 on Mar 10, 06 | 7:56 pm

Certifiable smart arse. I put up a first draft of a response, then took it down as I'm going to have to think further about this. Which is not to admit I am wrong - you are certainly misguided if think that double staircase of yours is a double helix...

Anyway Singapore is a piece of shit, that still holds true.

Your turning helical travellator concept is simply an example of an Archimedean Screw, isn't it?

Posted by: expat@large on Mar 10, 06 | 10:32 pm

Yes, an Archimedean screw. Exactly! Just what I was thinking of... Of course...

See figures IX and X in the following image...

Note how the step is present on both sides of the central fixture in figure IX...
The two steps are each like one of the base pairs in the DNA strand.
When a series of these pieces are strung together, you get a double helical staircase, as in figure X.

If each of these staircases had a handrail on the outside then these two outer handrails would be analogous to the two blue strands on the DNA diagram.

In short, There is no 'inner handrail' on the strand of DNA, at least on the diagram you provided... If there were, it would be a much more tightly wound strand, appearing very close to the centre. Also, when stretched out, this strand would be much shorter than the outer blue strands.

Now, what I cant get my head around, is whether my Screwed Archimedean Bridge would be able to deliver traffic in both directions at the same time... I think it can. However, no matter how many times I twist a texta in the air to visualize how it would work, I cannot convince myself that one direction wouldn't have to travel upside-down or something...

Can you see it? This smug son of yours is stumped for once...

Posted by: rambeaux2 on Mar 11, 06 | 11:47 am

And rightly so.

For those of you wondering what is going on here, the Son@Home and E@L are having one of their typically confusing discussions about absolutely trivial and inconsequential arcana.

After a 1hr phone conversation we have sort of come to the conclusion that we both might be wrong, or at least less right. He might no admit that, but I have the power to edit his comments...

The one final analogy we could both agree on was: if you twisted a small ladder like structure into a spiral (the PRIMARY helix), and then twisted THAT structure around your finger (the SECONDARY spiral), then that would be a double helix...

Which unfortunately for our analogy is not what DNA looks like.

Which is not to say that the bridge is right... Or maybe it is...

Maybe the double helix DOES refer to the two strands and not the spiral within a spiral...

Oh anyway, I have to pack for Thailand.

Posted by: expat@large on Mar 11, 06 | 1:56 pm

Hey folks.. Guess what...
I was right!

Posted by: rambeaux2 on Mar 12, 06 | 6:38 am

Still packing.

OK. That Wiki explanation explains thing much better than you did... (nudge nudge)

In the Vatican photo, the staircases don't touch the centre. That's where you were losing me with your description. They are two seperate staircases in the same stairwell, at 180 degrees out of phase, and this what threw me.

But yes, I am slowly getting it, I think.

They WOULD have touched at the centre if the well had not been been there - like your earlier diagram - but the space of stairwell has been removed in the centre, cored like by an apple corer.

But that is only the case because the Vatican staircases are 180 degree out of phase.

With the DNA molecule, the phase is much less, say 90 degrees, so the steps of the base pairs do not go through the centre.

Which is why you analogy wasn't working for me at first. Becasue if you cut out the centre of the stairwell in a DNA molecule, it doesn't make two seperate staircases: the base-pairs would still be contiguous across the space between the two strands. Unless you took a REALLY biug core out of the apple.

And the two strands are what people DO refer to when they talk about the DNA molecule. Each "sugar phosphate backbone" is a helix, as the Wiki says.

OK, I was wrong; its not a helix with in a helix after all.

But I still reckon the bridge is fucked as the walkway is totally indepentant of the structure of the supporting "helices".

Posted by: expat@large on Mar 12, 06 | 8:46 am

Ok, its all about the primary structure.
FORGET the secondary structure, for now...(Until we get back to the design of the bridge.)

The actual width of the central post of the staircase I was discussing is of no importance. It is a concept, a variable in the generalized model of double helices. It is of variable width.

Also the phase is not important. It is another variable... You could have a triple, quintuple, whateverupple helix staircase. The dna molecule is an instance of a multiple heliced, multiphased structure based upon a central core of variable width, and variable secondary structural orientation.
In short, do not get caught up in the physical implementation details - it is the pattern that matters.

In the dna molecule the steps do go through the logical/conceptual centre (which is of zero width). Split the molecule into its two strands, and you have the steps. The point at which the pairs meet is the logical central post.
Each of instance of Adenine, Thymine, Cytosine, and Gyanine are individual steps. By virtue of the fact that they meet everystep of the way, they must be in phase.
Ideally, the DNA molecule is not like a fucked up zipper.

Now... The Bridge... Can it be built as a Rotating Screwy Archimendedhistrousers structure, and allow people to travel in both directions on different strands or no?

A free voucher for the first person who can explain why it can or cannot...

Posted by: rambeaux2 on Mar 12, 06 | 10:23 am

Hmm... There I go getting caught up in the physical implementation details after all...!

Posted by: rambeaux2 on Mar 12, 06 | 10:24 am

I doubt anyone understands (!?!?!) where we've going with this, and I REALLY doubt that anybody cares...

Posted by: expat@large on Mar 12, 06 | 11:21 pm

So, who's in you guys Final Four?

Posted by: Tom on Mar 16, 06 | 4:44 am


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