[gladbach]

hi,
me and my roommates had an interesting discussion today, and because we are all mechanical engineering students we don't have a lot of knowledge about it. The question was if external influences, no matter how big or small they are, can change your DNA. For example if i work at a nuclear powerplant, something in my dna shifts and that way my dna would be different from the one i had when i was born. We thought it might locally be possible, for instance if you would have a tumor the tumor's dna would slightly differ from the dna around it.

And if so, is it possible that your children inherit that modified/different dna?

Kind regards

[jeffrey.struss]

You have to remember, your DNA is not a single entity per se. In reality it is millions and millions of individual copies of a single entity. Each of these copies can mutate independently of each other. That is how cancer that is caused by genetic mutation happens. One of these copies mutates into a cancerous form.

As for passing it on to future children, see above, but with additional caveats. It is very rare to see mutations induced in the reproductive cells like sperm and eggs. Most of the time when these have a mutation induced, the cell dies. This is what I remember from my radiochem class.

[rjb]

Gladbach,

There are many internal and external factors that can cause mutagenesis within the human genome. However our bodies have evolved some pretty incredible biochemical systems to mitigate the effects of these, and there are a whole host of enzymes designed to protect against specific chemical and biological mutagens. Damaging mutations that get past all of this are subjected to further mitigation by the enzymes such as perforins, which in some cases are able to destroy rogue cells.

There are a whole host of unpleasant chemicals that can alter DNA structure, often by either acting as base analogs, altering base pairing or intercalating with DNA. In most circumstances the body can to some extent deal with this, but not always, leading to mutagenesis. Another obvious cause of mutagenesis is radiation, be it ionising or otherwise. A nice example is UV, which is linked with skin cancers. Again the human body deals with mild UV irradiation to some extent using nucleotide excision repair enzymes designed to repair damage. In a few individuals, the enzyme/s are not produced leading to a condition known as Xeroderma Pigmentosa which results in individuals unable to repair UV damage and hence are unable to leave the house by day without risk of skin damage/skin cancers! 

In terms of heredity, that's an interesting question... Mutations within certain regions of the genome are quite common and we do come across them in paternity work. The mutation rates for common STR (short tandem repeat) regions in the genome (used in paternity testing/DNA profiling) can be as high as 0.64% for some markers, but this level of mutation is by no means representative of the entire genome.

I guess, in answer to your original question, on balance, your genome is the same as the one you were born with.

Hope this Helps

Kind Regards

R