Talk:DNA

M. F. Wilkins, Erwin Chargaff and Raymond Gosling's photos added

Not only Professor Wilkins's photo should be present but also

Professor Raymond Gosling's, Erwin Chargaff's, as well as the photos of Herbert Wilson. F.R.S. and Alex Stokes should also be present; however, the latter two were unavailable at this point for Wikipedia use, and if made available it is important that they also should be added because of their very important role played in the X-ray+molecular modeling analysis of DNA saga. Bci2 (talk) 4:26, 15 May 2009 (UTC)

Edit request

{{Edit semi-protected}} Please correct the spelling of the word "axis" in the second sentence of the "Properties" section.

Change from:

....As first discovered by James D. Watson and Francis Crick, the structure of DNA of all species comprises two helical chains each coiled round the same access, ....

to:

....As first discovered by James D. Watson and Francis Crick, the structure of DNA of all species comprises two helical chains each coiled round the same axis, ....

75.40.216.62 (talk) 16:09, 12 November 2010 (UTC)

Oh, wow, what an awful mistake D:

Corrected. ~rezecib ^(talk) 16:33, 12 November 2010 (UTC)

Arsenic based DNA

Suggest entire alternate DNA structure section be rewritten from scratch to include arsenic backbones in light of new research published today. —Preceding unsigned comment added by 64.124.22.9 (talk) 19:00, 2 December 2010 (UTC)

Agreed; this is a HUGE finding. See these references:

Subsisting on Arsenic, a Microbe May Redefine Life, By DENNIS OVERBYE, New York Times, December 2, 2010

http://www.nytimes.com/2010/12/03/science/03arsenic.html?hp

Arsenic-Eating Bacteria Opens New Possibilities for Alien Life

Henry Bortman, Astrobiology Magazine, 02 December 2010, 12:44 pm ET

http://www.space.com/scienceastronomy/arsenic-bacteria-alien-life-101202.html

The discoverer of this bacteria is Doctor Felisa Wolfe-Simon. Her website is this:

http://www.ironlisa.com/ —Preceding unsigned comment added by 208.252.16.225 (talk) 19:22, 2 December 2010 (UTC)

I just created a new sub-section in this article, Alternate DNA chemistry. Much of the exact text I used was borrowed from other material recently contributed to other Wikipedia articles. The problem with all those new (and useful!) contributions) was that they were scattered around several articles. This article, instead, seems the logical place to bring together and summarize the basic information. Details (which will certainly run to several pages) may then develop on other pages linked to this one. RK (talk) 18:02, 3 December 2010 (UTC)

The problem with arsenate in DNA is a much higher rate of spontaneous hydrolysis leading to DNA strand breakage (Why nature chose phosphates. Westheimer FH. Science. 1987 Mar 6;235(4793):1173-8.PMID: 2434996; Formation and properties of sugar arsenate esters. Lagunas R. Rev Esp Fisiol. 1982;38 Suppl:63-72.). Either this organism has enhanced DNA repair systems, or artificially high replication rates under lab conditions of growth manage to keep ahead of accumulation of serious chromosome defects. One consequence would be a higher rate of recombination events and resulting mutation, leading to selection of strains in the lab that tolerate the conditions. It would be interesting to compare the genome of wild-type bacteria from the lake with populations grown in the lab with minimal phosphate.96.54.32.44 (talk) 18:46, 3 December 2010 (UTC)

Good points. It I may throw this idea out there - this may just be a problem with standard DNA molecules incorporating arsenate, as seems to be case. This finding, it is being claimed, opens the door to entirely novel molecules - perhaps with different DNA (or RNA) bases altogether - being used as a genetic code. Such molecules, in their native environment, may be more stable than what we are seeing here in this first example. RK (talk) 20:27, 3 December 2010 (UTC)

Please note it is not proven that arsenic has replaced phosphorus in a working DNA. Write the section in the way that reflects this important fact. There is phosphorus still in the DNA even after being forced-fed arsenic.Hzh (talk) 13:55, 4 December 2010 (UTC)

In addition to that, there's no evidence this occurs in natural environments. It may be worth adding a section dealing with the finding that arsenate can replace phosphate in DNA in some experimental conditions in specific organisms, but it's not yet entirely clear how "mainstream" this theory is and how well-accepted it will be by the scientific community, so focussing too much on this is entirely WP:UNDUE. I'd suggest waiting a while until we actually have something to say about the significance of this discovery; as it stands all we have are greatly-exaggerated releases to the general public about the significance of this research, and little in terms of actual research papers and reviews. GiftigerWunsch [TALK] 14:27, 4 December 2010 (UTC)

"arsenic dna" as well as the currently popular term "arsenic based life" are not accepted scientific terms, and probably wont be. And, its true this is not fully peer reviewed or duplicated yet. I would recommend simply saying "hypothetical partial substitution of arsenates for phosphates within dna" instead of "arsenic dna". There is currently no "name" for this "thing" yet. We are surely not going to give it its name here. I know I dont get into peer reviewed journals, so why should i be allowed to coin a name for it on a group edited encyclopedia?(mercurywoodrose)75.61.136.242 (talk) 08:33, 6 December 2010 (UTC)

Alternate DNA chemistry

I edited the section for several reasons:

• The term "arsenic DNA" is not yet accepted by science, is potentially misinterpretable, and is subject to change. The piped wikilink is clearer and isolates this page from such a change.
• The original text ("...is the first form of life on Earth that may have arsenic DNA") was unclear; GFAJ-1 is not the first form of life with this ability, it's the first form discovered to (maybe) have this ability.
• Similarly, it's not the discovery of GFAJ-1 that lends weight to the As-backbone DNA hypothesis, as the original text had it. Rather, it's the discovery of its ability to (maybe) incorporate As into its DNA.
• Both "bacterium" and "bacteria" were being used with singular denotation.
• Without meaning to minimize Wolfe-Simon's contribution, her authorship of the study is incidental to this topic, so I moved it to the end.

Unconventional (talk) 18:21, 6 December 2010 (UTC)

Arsenic Hysteria

Everybody's too upset with that arsenic thing -> moreover: These bacteria were not grown on arsenic but on an arsenate medium, that's one important difference —Preceding unsigned comment added by 92.206.179.22 (talk) 18:21, 10 December 2010 (UTC)

Edit request: Rosalind Franklin

Could someone please remove the following silly sentences:

"DNA was discovered by Rosalind Elsie Franklin. However one of her neighboring scientists in the lab, Maurice Wilkins showed her photos without permission to Watson and Crick. She tried to beat them in getting DNA's structure and composure but they had overcome her."

 Done —Ute in DC (talk) 09:13, 18 February 2011 (UTC)

Edit Request

This article mistakenly implies that DNA is fully stabilized by Hydrogen bonding between base pairs, but recent science has shed more light on the subject. Far more stabilization comes from the reduction in Gibbs free energy due to base-stacking interactions which occur largely because the aromatic rings on the nucleotide bases are hydrophobic. It is in fact partially stabilized by hydrogen bonding but I wish the article to better reflect the true environment in the cell. You can read more at Stacking (chemistry). I am a undergraduate student at Michigan and I have heard this reiterated in multiple biochemistry lectures. I would like either permission to edit, or one of you Administrators who can edit this article to make the relevant changes. Here are my external Wikipedia-compliant sources:

• http://nar.oxfordjournals.org/content/34/2/564.short
• http://pubs.acs.org/doi/abs/10.1021/ja0692940

Ds2207 (talk) 00:10, 24 February 2011 (UTC)

I moved the above to the bottom of the talk page, which is where editors expect to find new comments. Please click "new section" at the top to start a new topic. I suggest you start editing the article! Johnuniq (talk) 00:44, 24 February 2011 (UTC)

And its done. I guess I misunderstood what Semi-protected means. Ds2207 (talk) 03:28, 24 February 2011 (UTC)

"Far more stabiliation comes from" base stacking? Wouldn't the Tm values for DNA melting be pretty similar between AT rich and CG rich be quite similar if that was the case? I'm sure base staking contributes to the stabilization but I'm a little dubious that it dominates. David D. (Talk) 17:59, 25 February 2011 (UTC)