Re: Re: Point mutations
Thu, 27 Aug 1998 22:49:18 EDT

In a message dated 8/27/98 10:44:09 AM, wrote:

>Radiation or free radicals mess up single nucleotides, changing them
>into other molecules, but I think the major contribution is errors in
>replication. If a single base is damaged (or just unlucky), the enzyme
>doing the replication might make a wild guess and insert a random
>nucleotide in the copy.
>Just a guess from a computer scientists playing molecular biologist :-)

Bingo. It's not that the base is changed directly into another normal base; it's changed into something else which causes the replication or repair system to put the wrong thing in.

Incidentally, the main cause of point mutations is copying errors *unrelated* to DNA damage. DNA replication is superbly accurate, with fewer than 1 error in a million bases (that's a 6-sigma process, which is normally considered perfection in manufacturing). But when you copy a genome of 4 billion bases, you still get hundreds to thousands of errors each time.