More intesting stuff....I'm leaving the email addys in these, in case you want to contact them directly....but this comment comes out of a thread that started with maybe folks in the South had higher mutation rates than in the North because of the heat...but I'm not sure outside heat as in weather would cause a mutation... But interesting stuff this...not that I understand all of it...but apparently heat will change the DNA structure... Char ----Original Message Follows---- From: Allen Blancett <[email protected]> Reply-To: [email protected] To: [email protected] Subject: Re: [DNA] Re: Cryptic Backup Copy of Genome - "Hothead Gene" Date: Thu, 24 Mar 2005 00:34:40 -0500 Bonnie Schrack wrote: > >My father, a physicist, had the following comment (hope he will not mind my >forwarding it): > >>Yes I saw the strange case of reversion to norm in the plants. Where else >>does it occur I wonder. There is one thing about DNA that I have never >>heard discussed. That is that all chemical compounds can be calculated to >>have a certain energy level. The compound is stable if the bonds are >>relatively strong compared to the random energy associated with >>temperature. At finite temperatures there is an occasional situation where >>there will accidently be sufficiently high energy available at a bond to >>break it. The compound will then collapse to a lower energy state. This is >>why, over time, many materials will disintegrate. If kept cold they would >>not. OK - now the case of DNA. Say there is a particular energy associated >>with a bond in the DNA. The higher the temperature the greater the rate of >>temperature induced mutations. But what if the mutation is caused by >>something that has sufficient energy to make a bond with higher energy >>than the original DNA structure ( like say -- radiation) . Then the new >>arrangement might well "disintegrate" back to the original un-mutated >>structure in time. > > >Could other scientists comment? >Bonnie Having lurked long enough, I'll jump in on this one. I'm not a scientist who figures out these things, but an engineer who applies the principles, including the last 21 years of my career in R&D on nuclear materials. Bonnie's father is right on the mark, I believe. This isn't even a stretch. It's true for heat energy, and it's true for radioactive decay energy. I'm sure the real scientists will correct me, but in a simple minded sense, the biological effects of radiation arise from energy of the radioactive disintegrations. The different types and strengths of energy (e.g., alpha, beta, gamma, 100 kEV vs 1.5 MEV) affect biological systems in different ways. Some of the effects, particularly at low doses, are reversible. In fact, there is an effect that causes more bickering than why we should or shouldn't split this list. It's called hormesis, and I think of it as analogous to muscle-building. A big dose of radiation can kill you (and so can a big enough dose of water), but a small dose appears to be beneficial, as though it stimulates the body's repair mechanism--sort of the way exercising strengthens the muscles for more exercise. Mutations don't just happen--they are caused. We just don't know all of the causes and their relative contributions. I believe stereochemistry is likely to play a role. In another simple analogy to simplify stereochemistry, think of two little bar magnets like the ones beneath the black and white dogs some of us grew up with. The attraction between the dogs depends on how they are oriented relative to each other. Extending from other areas of knowledge, I suspect strongly that different arrangements and combinations of A, C, G, and T in the chain will cause stronger and weaker chemical bonds varying along the chain. Some will mutate more easily than others. I don't know, but maybe the body corrects most of them but not all. I have no difficulty with the concept that reversion to a lower energy state may reverse a mutation spontaneously. Or a high-energy transfer might split the bond irreversibly. The nice thing about it is that I can use the mutations to help sort out my ancestors. I'm eager for another group of researchers to validate this reported finding. The interesting part for me is where the unmodified code may lurk so that it can repair the mutation and restore the attributes of the earlier generation. Allen ============================== Search the US Census Collection. Over 140 million records added in the last 12 months. Largest online collection in the world. Learn more: http://www.ancestry.com/s13965/rd.ashx