Re: DNA - Can you enlighten?

WJhonson@xxxxxxx wrote:
In a message dated 1/17/06 2:15:54 PM Pacific Standard Time, mcdonald@xxxxxxxxxxxxxxxxxxx writes:

<< There is a 50% chance the WAS one >>

I do not believe that there is 50% chance that *each* generation had a Y-chromosone mutation. If you think there is, provide a scientific journal article which states that.

Thanks
Will Johnson


for a review of mutation rates see http://www.kerchner.com/dnamutationrates.htm

Kerchner, though an amateur, really is the expert on this number.

For a good textbook with a discussion of this, see Jobling, Hurles and Tyler - Smith's book, "Human Evolutionary Genetics". I can't quote the
actual number from this book since my copy is at home.

The SNP mutation rate of chromosomal DNA is, on average, about
2e-8 per base pair per generation. There are about 4e7 bases on the
Y chromosome, so by these numbers the probability of an SNP
per generation is 0.8. This estimate is on the high side, since
some of those mutations will be fatal. Others will be useless,
as they will occur in unsequenceable heterochromatin. Thus
the round number 0.5 probability of a useful SNP per live birth.

The mutation rate is somewhat controversial. It probably is actually
somewhat higher than the number I quote.

One should add that currently for people in haplogroup R1b, currently
one family in 50 being tested for new SNPs has one ACTUALLY FOUND that
is probably unique to that family. (Source: David Faux, whose
company is doing the testing.) And this is testing only a teensy
fraction of the Y chromosome. Note that this is not for a mutation
in this single generation ... it's some unknowable distance back
in the line, basically back to the last great radiation of R1b
some few thousand years ago.

Doug McDonald
.

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