Re: junk DNA or buffer DNA?

Geoff Smith (
Tue, 17 Mar 1998 12:23:08 -0800

> From: Hal Finney <>
> To:
> Subject: Re: junk DNA or buffer DNA?
> Date: Tuesday, March 17, 1998 10:34 AM
> I don't see how that would work. Just adding more junk DNA will not
> reduce the number of mutations in the coding DNA. The mutation rate is
> presumably constant per base.

This may be a bad presumption. I have seen many assume that mutation rate
is constant per base, but I have never seen a validation of that
assumption. If mutagens are in any way significant in causing mutation,
mutation rate will not be constant per base, as the amount of most mutation
is not directly related to the number of base pairs. (eg. UV radiation) I
would assume that for these mutagens, number of mutations has a greater
relation to the amount of mutagen than the number of base pairs.

Still, I'm not sure if I totally agree with junk DNA being a buffer... why
would you want to lower the rate of mutations? Populations are genetically
stagnant enough already, and mutation is pretty low with or without
introns. Also, why do frogs have many introns (even though they are mostly
protected from UV by water), while birds have very few (even though they
are flying through lots of radiation)?

> Adding N times as many bases will make
> sure that N/(N+1) of the mutations occur in the junk region, but there
> will still be the same number occuring in the coding part.
> Hal