> Pete, approximately how many generations of mice are there per year?

In the original post they state:

> After 40 generations of brother-sister matings, a feat that might be accomplished in a decade.

Mice can have litters every three weeks but the males need to be at least 8 weeks old to mate. Hypothetically, you could create more than four generations per year, but in practice that would be the norm.  

I would suppose that the rate of mutation would be different for different species. Also, with mice they are talking about noticeable mutations (phenotypes). There may be many more silent mutations they do not express right away or even at all. 

The use of SNPs (single base pair copy error) as a molecular timepiece assumes a constant rate of mutations, but the SNPs do not necessarily affect the functioning of the organism. Genetic drift is predominantly neutral -- very occasionally generating beneficial or harmful changes. 

PLB

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