classic genetics question (Gustavo A. Seluja)

"kleinh01 at" at MCRCR6.MED.NYU.EDU "kleinh01 at" at MCRCR6.MED.NYU.EDU
Tue Jul 15 10:48:42 EST 1997

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Subject: Re: classic genetics question (Gustavo A. Seluja)
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From: Hannah Klein <kleinh01 at>
Date: Tue, 15 Jul 1997 09:08:49 -0500
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Organization: Dept. of Biochemistry, NYU Medical Center
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Graham Dellaire wrote:
> Okay I will bite!
> TWO BROTHERS are more genetically similar.
> Here is my reasoning.
> Lets say the whole compliment of genes from Mother or Father is half
> each of their respective parents (P1F P2F and P1M and P2M for
> mother...etc)  so:
> Father is 50% P1F and 50% P2F and Mother is then similar with 1/2 P1M
> and 1/2 P2M
> So the F1 of their cross (which are the brothers in question) are 1/4
> P1F, 1/4 P2F, 1/4 P1M and 1/4 P2M on average (remember treating the
> haploid compliment of each parent as a whole).
> The brothers are identical in this respect, where as the father does not
> have P1M or P2M alleles (unless this is consanguinous then that is a
> whole new ball game...<smile>).
> So the two brothers are more alike genetically.
> Graham

A father and son share exactly 50% of their genetic material.  Two
brothers can share from 0% to 100% of their genetic material.  On
average two brothers are 50% identical.  For any given allele from a
parent that one brother carries, the other brother has a 50% chance of
having that allele.

Hannah Klein
kleinh01 at

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