Re: longevity
Sat, 20 Nov 1999 17:20:17 EST

In a message dated 11/19/99 10:29:35 PM Pacific Standard Time, writes:

> Thank you for the information. Apparently, modifying the genes of mice can
> extend their life span. If identical modification happened as a result of
> mutation rather than engineering, would the mutant individual have a
> advantage?

Yes, provided there were no disadvantages. If the effect were small it could still be
lost through drift (bad luck) but 30% is a lot, even late in life.

>Could such a mutation occur naturally in millions of years of mice
generations? --J. R.

There are billions of mice in the world, and each one carries a few dozen point mutations from the previous generation. So any 1-base mutation is happening several times a year. Since this is a loss of function, dozens of mutations (loss of the start codon, any splicing goof, most additional stop codons, a couple of significant base changes, and deactivation of the promoter) would produce the phenotype.

Of some relevance is work John Tower did on increasing antioxidant activity in flies. Some lines got better, some got worse, and some had no change. This kind of mutant won't necessarily have a big advantage. On the other hand, you wouldn't want to take a drug for this effect without screening - what if you're one of the lines that loses?