I used a rate for mutation taken from Gish. THere may be better rates of
mutation out there, but I choose often to quote from apologetical books,
because the people I am trying to influence usually believe those books are
the best. The rate was 1e-7 per nucleotide location per generation. This
means that any given location in your genome has a 1e-7 chance of having a
nucleotide that your parents didn't have. Thus when you multiply this by the
3.5 billion nucleotides in the human genome, it is quickly realized that we
should not be smug and call a friend a "mutant". We are all mutants many
times over.
But given the assumption that a given gene, whose coding portion is 999
nucleotides long, which codes for a 333-unit-long protein, what are the odds
that one of these mutations will lie in exactly that portion of the genome?
You have 1000 x 1e-7 = 1e-4 which is the odds that in the generation that
created you, you will have a mutation in a given protein. This mutation, may
not code for a different amino acid, in which case you will not have a
different protein. Some amino acids have 6 nucleotide triplets which
call for them. But as Terry noted, even if it does cause a substitution, it
may not alter the function of the protein because there are many substitutions
in a given protein which do not alter function.
With that as a back ground, a generation is, well, a generation-parent to
child.
I do not know how common the alleles are in the population but that is not
relevant to the problem at all.Let me illustrate two alleles, using letters in
place of nucleotides.
allele 1
abbdcbdabcdbabdbad
allele 2
aabbabdabccbabdcdd
If I counted correctly there are 6 differences between these two very short
alleles. If the logic of the situation requires that allele 2 be derived by
random substitution from allele 1 then what you have is one of those puzzles
I can never do, in which you are asked to go from the word "wore" to "bass" by
making a one letter substitution at each step always having a real word at
each step. In other words you can't have "wors" because that is not a word.
wore-ware-wart-dart-dare-bare-bars-bass
This is how allele 2 must be derived from allele 1. If a substitution gives a
"non-word" like "wors", e.g. a harmful gene, then the guy dies without leaving
offspring.
We know the probability of a substituion at each location each generation, so
it is mere probability to look at allele 1 and tell how long (on average) it
must have taken to derive allele 2. With six substituions, the odds are that
it took 60,000 generations to make the six substituions. Since human
generations are 20 years or so, then 20 x 60,000 = 1,200,000 years.
The global flood advocates have only two mice on board the ark, and yet there
are 92 alleles a location of the MHC complex of mice. Thankfully mice
generations are of the order of weeks but that still requires a huge span of
time.
All 59 alleles must be derived from parent-child mutations from the 10 alleles
on the ark. They must be derived in a pattern in which each gene on the ark
gives rise, on average to about 6 mutated genes today.
Thus, the flood, MUST have been at least as long ago as I
suggested. I know thata lot of people have a gut reaction against such a view
but, I explain 99% of the data by having it there. They explain nothing with
the currently accepted view.
Jim wrote:
>>I'll frame the same question in a different way. Let's take the world's
population to be 5 billion. Let's say an allele has to be in 1/10,000 people
for it to make it into the class of 59. Then 500,000 people have that allele.
Are you asking me to accept that there is a 1/1,000 chance that 500,000
people will be born with the same mutation in the same generation?"
No I am not asking that you believe that. I am a little unclear what you
are asking here but why should that stop me from answering. :-) First, an
allele is not simply a one locus mutation. It can be, but what is apparently
observed in these alleles is that there are multiple substitutions between the
alleles. Each substituion constituted one mutation. The time for x
substituions to accumulate must be calculated based upon the observed rate of
substituions.
Jim wrote:"If on the other hand, by generation you mean 1 child per parent,
and the commonality of the allele is not an issue, then the number of alleles
in the population clearly depends on its size, which somehow doesn't figure
into your calculation."
The concept that the number of alleles is depended upon population size seems
to be a common misconception. Let me try this. A gene is a location on the
genome. Mathematically consider it a slot into which you can slide a number
ofdifferent objects. The objects which can be slide into these slots are
alleles. You have about 100,000 genes. Since you have two copies of each
gene, you can have two alleles (if you want) at every one of your genes. But
you can not own more than two alleles at any slot, unless you have
extrachromosomes and that is usually bad. In the population everybody has the
same 100,000 genes, but they don't have the same alleles, stuck into those
genes(position). There could be thousands of alleles, but any individual can
only have two of them. And you MUST have gotten YOUR alleles from the 4
possible alleles you parents could have had between them. Thus you and your
siblings share a large number of common alleles. That is why you look alike.
Thus, in your family your parents and siblings you are not likely to have any
novel alleles between you all at any given genetic location. The increase in
your families population did not increase the number of alleles significantly.
Your parents had 4 max and you had to recieve yours from those 4. (I was once
criticized for using a "slot" analogy to explain genes, it is only avisualizat
ion tool).
Does this help? Maybe a Biology Prof can give a short lecture on the
difference between alleles and genes in a way that is better than I can do?
glenn