Talk:Indirect DNA damage

Sources

Sources needed for all claims per WP:V. Unsourced material will continue to be removed. TheRedPenOfDoom (talk) 22:59, 16 May 2008 (UTC)

As it states in WP:V, sources are only needed for "any material challenged or likely to be challenged". You are removing informative material which has not been challenged, and you have provided no reason why it is likely to be. I am restoring the material, along with a "citation needed" tag.

Yes, in the future it will be nice if we get citations. The article certainly won't attain "good" status without them. But for now, this is a young article, and it is unreasonable to require every single claim to have a source.

The existence of the "citation needed" tag implies that at least some unsourced material is allowed to stay in Wikipedia. It is therefore necessary to provide a better reason than "unsourced" for removing material. I am happy to discuss this with you further if you disagree. Njerseyguy (talk) 16:48, 14 July 2009 (UTC)

Yikes. On second thought, I am going to collect the reverted edits below rather than put it all back in, because that is a huge job. Njerseyguy (talk) 17:13, 14 July 2009 (UTC)

The molecule which originally absorbs the UV-photon is called a "chromophore".

The bimolecular reactions can either occur between the excited chromophore and DNA, or between the excited chromophore and another species to produce [[free radical]]s and [[Reactive Oxygen Species]]. These reactive chemical species can reach DNA by diffusion and the bimolecular reaction will damage the DNA ([[oxidative stress]]). Importantly, indirect DNA damage does not result in any warning signal or pain in the human body.

The mutations which result from [[direct DNA damage]] and those which result from indirect DNA damage are different, and genetic analysis of melanomas can elucidate which DNA damage has caused each respective skin cancer. Studies using these techniques have found that 92% of all melanoma are caused by indirect DNA damage and only 8% of the melanoma are caused by direct DNA damage.<ref name=Davies> {{cite journal |author=Davies H.; Bignell G. R.; Cox C.; |year= 2002 |month=6 |title= Mutations of the BRAF gene in human cancer |journal= Nature |volume= 417 |issue= |pages=949-954 |id=

==Effect of Antioxidants==

The primary mechanism of indirect DNA damage from the sun is from the hydroxyl radical, and the singlet oxygen radical as shown above. Antioxidants can interfere with this process by being preferentially oxidized by the free radicals, thereby saving the DNA from being damaged, and quenching the chain reaction before it begins. (See articles on free radicals and antioxidants for supporting evidence of this mechanism)

==Location of the damage==

Direct DNA damage is confined to areas that can be reached by UV-B light. In contrast free radicals can travel through the body and affect other areas - possibly even inner organs. The traveling nature of the indirect DNA damage can be seen in the fact that the [[malignant melanoma]] can occur in places that are not directly illuminated by the sun - this is in contrast to [[basal-cell carcinoma]] and [[squamous cell carcinoma]] which only appear on directly illuminated locations of the body.

By the way, I am going to go ahead and challenge the "Effects of Antioxidants" material. It sounds like it's POV along the lines of Free-radical_theory, which is very controversial. Njerseyguy (talk) 17:13, 14 July 2009 (UTC)

The claim "free radicals can travel through the body" is still in there, and still unsubstantiated. While technically true, it is misleading. Since the free radical will react with the first thing it bumps into, the probability of it travelling any significant distance is infinitesimally small. The sentence "Importantly, indirect DNA damage does not result in any warning signal or pain in the human body." also gave me pause. Firstly, why is this so important? Secondly, where are all the people who are expecting to feel pain when they incur DNA damage, and is this the appropriate place to correct them of their misapprehension? Thirdly, wouldn't the body's mechanisms for DNA repair and apoptosis of cells with faulty DNA constitute a "warning signal"? --60.36.179.50 (talk) 07:27, 24 March 2011 (UTC)

Title

As per the comment I made on the direct DNA damage discussion page, the title for these articles needs to be changed, as there are many more ways of direct and indirect DNA damage than just UV radiation. Philman132 (talk) 11:18, 3 May 2009 (UTC)

Completely agree with this. I think this page must be changed, either the title, or what's included in it. It simply cannot stay as it is. Hzh (talk) 11:07, 12 October 2011 (UTC)

Indirect DNA damage citation

I think the statement "92% of all melanoma are caused by indirect DNA damage " needs citation because the Nature paper referenced by this article doesn't make this claim. Davies et al. writes:

"The highest frequency of BRAF mutations is in malignant melanoma (Table 1). This does not seem to be related to the effects of ultraviolet light, the only known environmental risk factor for this disease. The T -> A change at nucleotide 1796, which accounts for 35 of 38 (92%) of BRAF mutations in melanoma (Table 1), is distinct from the CC -> TT or C -> T changes associated with pyrimidine dimer formation following exposure to ultraviolet light—these changes are commonly found, for example, in the TP53 gene in non-melanoma skin cancers7."

The Nature paper only claims that 92% of BRAF mutations in melanoma are caused by a T -> A change at nucleotide 1796. While this BRAF mutation may be caused by indirect DNA damage, the authors make no claims that this particular mutation is resposible for 92% of melanomas. Biochemallurgist (talk) 21:10, 21 November 2010 (UTC)

Melanoma

Melanomas are well known to mestasize, the presence of them elsewhere than the skin may be due to this rather than travelling free radicals Polypipe Wrangler (talk) 04:42, 7 April 2020 (UTC)

Also, sun damage is not the only mechanism for DNA damage. There are non-skin melanomas (oral, rectal, etc) that don't appear to be associated with sun exposure or UV light at all, so their existence on un-illuminated skin doesn't necessarily need to be explained. Of the universe (talk) 20:02, 7 April 2020 (UTC)

Melanin half-life

The stated half-life of melanin excitation is questionable. The cited source is about the half life of DNA excitation not melanin. Another user tagged the sentence as dubious saying "I've done fluorescence lifetime imaging of melanin, and it tends to stay excited for nanoseconds. The 1 fs value is probably off by a factor of a million." Of the universe (talk) 21:53, 7 April 2020 (UTC)

Inner organ damage

I have been unable to find any discussion in reputable sources that substantiate the claim "reactive chemical species can travel through the body and affect other areas—possibly even inner organs." Another user, earlier in the talk section says "The claim "free radicals can travel through the body" is still in there, and still unsubstantiated. While technically true, it is misleading. Since the free radical will react with the first thing it bumps into, the probability of it travelling any significant distance is infinitesimally small." This other user's intuition matches my own, but I am not well versed in biology, so I don't know. Of the universe (talk) 23:33, 7 April 2020 (UTC)