Talk:Nucleic acid double helix

Different helix geometries

This section is wrong in many ways. I have already gone through this in the main DNA article. There are not only three types of double-helical DNA (there are A-, B-, D-, C-, E-, G-, H-, and Z-forms, just to name a few) and they do not differ "modestly". Z-DNA differs so much from B-DNA (e.g. it winds to the left and in a zig-zag pattern) that it is used precisely as a form to show just how much DNA can differ from the commonly understood right-handed, smooth backbone form. I have changed this many times, but over and over again people continue to change it back to say "they only differ modestly". --Thorwald 02:27, 23 December 2006 (UTC)

• Do you have a good reference for this? (i'm interested!) - Zephyris _Talk 12:59, 31 January 2007 (UTC)
  • Which part? That DNA is known to adopt many different forms, or that these form do not "differ modestly"? If the former, my references are already listed in the main, DNA, article. If the latter, just look at the tables in this article, the DNA article, or the Z-DNA article; they all show just how much the geometries of these forms differ and include references to back these data up.--Thorwald 00:02, 5 February 2007 (UTC)

Rewrite

I have carried out a massive rewrite of this article, and all the info which used to be there should still be there... plus more! I realise it is essentially unreferenced and when i have more time it will collect some references. I ask ppl to read it and correct my appalling grammar and spelling! :) - Zephyris _Talk 20:09, 31 January 2007 (UTC)

Future of the article

This article is quite long and has kind of lost purpose, any suggestions from anyone on what should be done with it? - Zephyris _Talk 15:08, 4 February 2007 (UTC)

• I think the article is fine for now. If fact, I would be in favour of expanding it even further. The title of the article is, after all, "Mechanical properties of DNA". This is a huge subject and this article barely scratches the surface. I always find it interesting that people are constantly promoting less information on Wikipedia (not saying that is you).--Thorwald 00:02, 5 February 2007 (UTC)

My biggest concern is the overlap of DNA with mechanical properties of DNA and the 'isolatedness' of this article - it only has 5 pages linking to it! But im definately not in favour of getting rid of any information :) - Zephyris _Talk 00:58, 5 February 2007 (UTC)

Integers discussion

[The main problem with this equation is that it is dimensionally flawed. An integer is stated to be equal to the sum of two real numbers. This is impossible. An integer can only equal the sum or difference of integers in such an equation. Thus changes in the expected twist seen in crystallographic studies of nucleosomal DNA (see later) cannot resolve this incompatibility between integers and sums or differences of real numbers.]

Can anybody find some sort of source for this comment? Tim Vickers (talk) 19:09, 28 October 2009 (UTC)

Tim, Mathematically, integers can always be represented as the sum of two real numbers, but the sum of two real numbers are not always integers. For example, the sum of pi + pi is not an integer, but the integer 1 can be represented by the sum of real, non-integer numbers 1/3 and 2/3. I have no idea how this relates to crystallography, though. —Preceding unsigned comment added by 159.189.224.217 (talk) 00:30, 23 April 2010 (UTC)

I just removed a similar statement which was recently added: "(The main problem with the equation L = W + T is that it is dimensionally flawed. L is an integer and W & T are real numbers. Real numbers cannot be added together to produce an integer. This problem has never been addressed even though several authors, like Schleif, and Delmonte, for example, have commented upon it. Any topological deductions drawn by mixing up real numbers and integers are flawed and are of doubtful use.)" Antony–22 (^talk⁄_contribs) 22:21, 22 February 2011 (UTC)

Massive reorganization of biomolecular structure articles

This article was moved from DNA structure to Nucleic acid secondary structure as a result of a proposal at WT:MCB. DNA structure now redirects to Nucleic acid structure instead. Antony-22 (talk) 20:36, 10 April 2010 (UTC)

Phase II

This article was moved from Nucleic acid secondary structure to Nucleic acid double helix, and then the article was split with some material moved back to create a new article at Nucleic acid secondary structure. The split was done this way to keep the edit history at the article containing the larger portion of the split. Then, Double helix was merged into this article. Antony-22 (talk) 01:05, 30 April 2010 (UTC)

Double Helix

Double helix is a geometrical structure outside of nucleic acid. Why isn't there an article simply about The Double Helix as well? Why should "double helix" direct me the the structure of nucleic acid, something which just so happens to be in the shape of a double helix? —Preceding unsigned comment added by 206.248.167.220 (talk) 11:37, 2 October 2010 (UTC)

There is a disambiguation page at Double helix (disambiguation), which in linked in the hatnote at the top of this article. The truth is, almost all of the incoming links to Double helix mention it in the context of DNA, so it would seem more appropriate to send those links here rather than the disambiguation page. Antony–22 (^talk/_contribs) 03:57, 3 October 2010 (UTC)

Is really chromosomic DNA negatively supercoiled in most organisms?

There's no reference for such statement and it is very imprecise. What does most organisms stand for? in biomass? in number of species?, it means most prokaryotes? (at least I would agree with that). From the way in which the DNA is 'twisted' around nucleosome cores, solenoids and the higher levels of DNA packaging it follows that nuclear eukaryotic DNA is most likely positively supercoiled. Nucleosomic DNA has 10.17 base pairs per twist whereas the relaxed B-DNA double helix has 10.5bp. The tension generated is partially released by generating positive supercoils while decreasing the number of twists. Thus, negative supercoiling, i.e., with fewer twists than the relaxed B-DNA double helix, would be restricted to prokaryotes with the exception of extreme thermophils (with positively supercoiled DNA to to prevent dsDNA denaturation).Heathmoor (talk) 13:01, 24 June 2010 (UTC)

dsDna hydrophobic interior

Sci Am early 2010 wonderfully splendid colored large pictograph of space-filling model of ATP. Red at the polar phosphate [O-'s everywhere] end and blue at the other, turns out to be non-polar, end. Examining and extrapolating to the other Bases shows that dsDna is a LINEAR BILAYER! It must take a great deal of energy two separate the two strands. This brings hydrogen-bonding into a new light. Namely, that the inward force generated by two hydrophobic entities inextricably pulled together is least concerned with what hydrogen bonds/nucleic acids are to be included or added, and most concerned with those that must be excluded for everything to fit properly! ~ Betaclamp (talk) 06:38, 18 October 2010 (UTC)

This has been known for a while: dsDNA's stability mostly comes from base stacking and hydrophobic interactions (though the specificity comes from a combination of hydrogen bonding and sterics). It's even been shown (by Eric Kool I think) that a DNA analogue without any hydrogen bonds still forms a double helix.

This isn't covered very well in this article, though it is touched on in Base pair. It is likely a good additional topic to cover here. Antony–22 (^talk/_contribs) 23:27, 18 October 2010 (UTC)

Misleading caption on the lead image.

"Image of a DNA chain which shows the double helix replicating itself" is misleading, because DNA can't actually replicate itself, but requires a bevy of enzymes and cofactors to perform this function. How about "Image of a DNA chain showing the basis for replication of the sequence". 96.54.32.44 (talk) 08:35, 4 December 2010 (UTC)

Major and minor groove

Both Major groove and Minor groove redirect to this article. However, this article doesn't really explain what they are except for a sentence in the lead. I think that they are important concepts that deserve at least their own section and a figure in this article. Alexbateman (talk) 11:59, 5 April 2011 (UTC)

Agreed. I just copied a paragraph and a figure from the DNA article, but it could definitely be expanded further. Antony–22 (^talk⁄_contribs) 19:50, 5 April 2011 (UTC)

Citation 37 does not have the purported information

> major groove: 22 Å wide; minor groove: 12 Å wide. 2603:9000:F101:2C28:FCC2:8FD5:44B6:CC3C (talk) 21:21, 23 October 2022 (UTC)

Animated Png fails to move

The animated picture of the common B form of DNA

File:DNA orbit animated static thumb.png

fails to rotate, unlike the nice animations on the separate Z-DNA and A-DNA articles. Perhaps it is a browser-dependent problem (I use Mozilla) and the animation rotates for most users.CharlesHBennett (talk) 04:43, 19 January 2014 (UTC)

Base Pair Parameters Image

I really like it - it's a helpful illustration, but it would be nice if it were darker and not hand-drawn. I was originally wondering (due to the handwritten quality) if this was from a famous scientist's personal notes/diary. So it's fine, and can stay in my opinion, but darker and clearer would be nice.--Varkman (talk) 10:46, 24 March 2014 (UTC)

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Lead image is not a double helix

The lead image appears to be two helices one stacked on top of the other. They do not constitute a double helix, which are intertwined. The connecting base-pairing are thus very distorted from the true picture. This image should be replaced with a proper 3D image - Martin Vcpmartin (talk) 02:20, 4 July 2019 (UTC)

Have meantime uploaded a replacement to MediaWiki File:Double stranded DNA with coloured bases.png but haven't included it yet Vcpmartin (talk) 04:37, 4 July 2019 (UTC)

Good catch. Actually, there used to be a better lead image that got removed by an IP user in March 2018. I just restored that one while keeping the one you added; I think it's useful to have a simplified representation there too. Antony–22 (^talk⁄_contribs) 08:33, 5 July 2019 (UTC)

Abbas on the main line

I Am Boom of God 107.126.28.3 (talk) 09:15, 30 July 2022 (UTC)