Radiation Effects

[JMUCKERHEIDE@delphi.com]

Rob, 

> I was watching McNeil Leher news last night and a cancer researcher was
> discussing how a cell becomes cancerous.  Basically he said that some genes
> may indicate a persons susceptability to cancer but cancer will form after a
> series of DNA replication mistakes alters the gene.  He went on to say that
> there are a number of environmental (man-made and natural) factors that lead
> to these mistakes that are commonly occuring at some given rate.  Cancer
> develops when either the repair or cell rejection system in the body could
> not keep up or identify these cancerous cells at a rate sufficient to stop
> the growth.
> 
> My question is, what is the normal rate of replication mistakes or gene
> disruptions, and how does this compare to those induced by radiation.  What
> % of the natural rate would X rem/yr (cSv/yr) cause? 

Estimate of 10^39 DNA replications lifetime, 1 in 10^10 go wrong:  10^29 need
repair. 

One estimate puts routine damage events at 8000/cell/hour; and ionizing
radiation is 20/cell/cGy. 

> I am relying on my memory for the details above, please correct if the
> statement of the problem is inaccurate.

The explanation of cancer induction was somewhat simplified from what I heard
at the Victor Bond symposium last Nov from Dr. Trosko (Geneticist, U. Mich.
and former Research Director of RERF) and eg Dr. Sohei Kondo, at the ANS
Winter meeting.  See also the "Molecule of the Year" article about the DNA
repair proteins in Science, Dec 94. 

I'm also relying on memory. Let me know if you want refs, I'll try to look
them up. :-) 

> Yours,
> 
> Rob Gunter

Thanks.

Regards, Jim Muckerheide