Walter wrote:
>>Small correction. That genome size is for the human HAPLOID genome, that
is, it is the size of the genome carried by a human sperm (or an unfertilized
egg). The human offspring is diploid and receives mutations from both the
sperm and egg, thus doubling the mutation rate experienced by offspring.
Thus, by Glenn's own figures, each human progeny receives 2 x 3.5e9 x 1e-7 =
700 new mutations. <<
I replied:
>>Some biologist might want to correct me on this but since in DNA A combines
with T and C with G, the two strings are not totally independent of each
other. I have seen some reports that there are slight differences in the
mutation rates of the sense vs antisense strings of DNA but in general it is
my understanding that a mutation in one will normally be matched in the other
during cellular division. If this is the case, then your comment about
haploid/diploid is irrelevant to the problem.<<
I have been corrected. I messed up on the Diploid/Haploid definition here.
Walter is correct that the 2 copies of each chromosome can mutate
separately. I was thinking of the two strands that make up each chromosome.
I would like to ask some of the biologists on the reflector to get involved
here. We have me, a geophysicist, arguing with Jim Blake, an Electrical
Engineer, about genetics. Surely some biologist on this reflector took at
least one course on population dynamics and can lend an air of experience in
answering the very basic question which gave rise to this whole discussion:
Is there time for the abundant genetic variation we see, to have arisen in
the past 5,000 years, the past 100,000 years or do we need more time than
that?
I read things like
"Hence, assuming a past effective population size of 10,000 individuals and a
mean generation time of 20 years, the mean coalescene time of two neutral
genes now present in the human population is 400,000 years." - Klein,
Takahata and Ayala, MHC Polymorphism and Human Origins, Scientific American
Dec. 1993. p. 80.
and
"The antiquity of MHC allelic lineages contradicts the coalescence theory's
conclusion that all human alleles date back no further than 400,000 years.
One of us (Takahata) suggested in 1990 that the difficulty lies in the
theory's main premise, namely, that the genes in question are not neutral but
subject to balancing selection-a form of selection that keeps two or more
alleles in a population longer than would be expected if they wer drifting in
random manner." IBID.
These, while not necessarily supporting my math, do support the main problem
I have been discussing, That there has not been enough time to generate the
genetic variability. This is what I see experts in the field saying. The
math I, or Jim, used in general supports the proposition that the most recent
genetic bottle neck was far before the period of time most Christians place
the flood or place the creation of man.
So, are there any brave biologists who can avoid the stupid mistakes that I,
an amateur, am going to make and can give us a lesson in the math?
glenn