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Author Topic:   Reduction of Alleles by Natural Selection (Faith and ZenMonkey Only)
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Message 20 of 87 (553644)
04-04-2010 1:22 PM
Reply to: Message 18 by Blue Jay
04-04-2010 11:44 AM


Re: The crux
Bluejay writes:

I have twice referenced a paper that found approximately 60 new mutations in the genomes of two human children. If we assume 1-2% of the genome is coding DNA (i.e. genes), this means we should expect 1-2% x 60 = 0.6 new alleles per individual birth (this is genome-wide).

Just wanted to clarify how the math works.

If the 60 mutations are single nucleotide mistakes that occur randomly throughout an average individual's genome, then with 3 billion nucleotides that's a mutation rate of 2 x 10-8. If 1 to 2 x 10-2 of the genome is coding (i.e., 1% to 2%) and the number of genes in the human genome is 30,000, then one could reasonably expect the number of genes with new alleles to be around 1 most of the time, because the odds for one of those mutations occurring in an actual gene is .002% to .004%, times 30,000 genes, which is 0.6 to 1.2 mutations (which are new alleles) per individual.

There are about 130 million babies born every year, and so if there's approximately one new allele per individual then on average the human race produces around 130 million new alleles every year. Some number of those would be duplicates, but getting in the ballpark statistically on that figure would not be a simple calculation.

If a small group of a hundred individuals were to become trapped on an island then they would have around 1 or 2 babies per year (I'm assuming same birth rate as the world), which is 1 or two new alleles per year.

The question you two are currently discussing is how this rate of increase in alleles in this small population compares with it's rate of loss. The death rate in the world today is only about 40% of the birth rate, so barring catastrophe the population size will increase.


--Percy
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Message 35 of 87 (554434)
04-08-2010 9:30 AM


Moderator Suggestion
I think it is important to keep the focus on mutations until a common understanding emerges.


--Percy
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Message 40 of 87 (554636)
04-09-2010 11:43 AM


Moderator Request
Could we please return to more of a "Just the facts, ma'am" kind of discussion?

PS - The quote is a dragnet reference, which Faith might recognize and Bluejay might not.


--Percy
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Message 46 of 87 (554893)
04-10-2010 7:07 PM
Reply to: Message 44 by Faith
04-10-2010 5:19 PM


Re: RAZD and Ring Species -- wow what a miscommunication
Faith writes:

OK, I'll answer RAZD here instead of on the other thread:

My suggestion is that you focus on the discussion in this thread. You're still focused on the other thread, you're just posting your responses here instead, which is very confusing. If you choose not to follow my suggestion then you may as well at least post your replies in the correct thread.


--Percy
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Message 60 of 87 (554966)
04-11-2010 6:10 AM


The Road from Here
What would the participants like to do? I see two ways to go: I can either close this thread or replace BlueJay.


--Percy
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Message 73 of 87 (555750)
04-15-2010 9:04 AM
Reply to: Message 72 by Faith
04-15-2010 1:01 AM


Well, this isn't fair. ZenMonkey can take as much time as he likes, but it isn't fair to you that you have no posting permissions over in Biological Evolution while awaiting a response here, so I'm going to restore them for now.


--Percy
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Message 77 of 87 (556228)
04-18-2010 8:41 AM
Reply to: Message 76 by Faith
04-18-2010 12:09 AM


Re: Picking up from the other thread.
Hi Faith,

Just a clarification about something ZenMonkey said:

Faith writes:

Thus the odds are 50% that a mating will produce a black rabbit, at 25% chance that you get a grey, and a 25% chance that you'll have a brown rabbit.

Isn't it 50% black and 50% brown because brown is dominant to grey and grey to tan?

ZenMonkey didn't completely describe the dominance hierarchy, but it can be implied from the outcome he described. Here's his full dominance hierarchy:

Black > Grey > Brown > Tan

Or using his abbreviations:

B > G > R > T

Thus, Br mating with Gt can produce these allele combinations:

  • Black and Grey, and since Black is dominant over Grey: Bg
  • Black and Tan, and since Black is dominant over Tan: Bt
  • Brown and Grey, and since Grey is dominant over Brown: Gr
  • Brown and Tan, and since Brown is dominant over Tan: Rt

This means 50% Black, 25% Grey and 25% Brown.


--Percy
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This message is a reply to:
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