Wizards, Muggles, and Genetics (long)

[madlysarcastic]

No: HPFGUIDX 119729


Chame wrote:

The response she gave to the 
> question of Squibs recently contains a reference to a dominant gene for 
> magic, which means there is also a recessive gene which precludes magic 
> ability. To put this in context for us Muggle types, this is
similiar to 
> blood type genetics you learned in Biology:  A, B, AB, & O blood
types. A & 
> B genes are dominant over O, and a person's O blood type means that
both 
> parents gave the recessive gene together to their offspring.  O
blood type 
> genes are recessive, as is Squibness (hey! I made a new word!!!) :)
 I think 
> you might get the jist of where I'm going with this, but if you
apply the 
> same principle to Muggleborns - for instance, take Hermione and
Lily.  Each 
> had 2 parents who gave them the dominant magic gene . How does THAT
happen? 
> Here's a thought:  wizards in Hermione & Lily's parents' lineage way
back 
> when?
> 
> In my mind, here's the real question:  is the recessive nonmagical
gene a 
> MUGGLE influence, or did pureblood wizards have it all along?


Maddy writes:


Yay! I'm not the only one who got all excited and starting pondering
the genetics of the wizarding world...

I must admit though, I hadn't thought about muggle borns until you
mentioned it now. But if the magic gene is recessive, then I can't see
how Muggle borns happen. Even if Hermione's and Lily's ancestors had
wizard blood, it would have been passed on without skipping any
generations, and then that would mean that they weren't muggle born at
all.

(beware...I'm going to go into bio-speak, here, but I think it makes
sense even if you don't know much about genetics)

If we let "M" and "m" represent the alleles for magic (M) and
non-magic (m), with "M" being dominant and "m" being recessive...

mm = the genotype of a muggle or a squib
Mm, MM = the genotype of a witch or wizard

mm X mm = mm (Two muggles or squibs will only end up producing
non-magic children)

Where as:
Mm x MM = Mm, MM
MM x MM = MM
Mm x Mm = MM, Mm, mm
(Witches and wizards almost always produce magical children.)

With that I would think that Squibs would be a bit more common...and
how do muggles with "mm" recessive magic genes spontaneously produce
"Mm" or "MM" magic children?

Unless it's possible to carry the magic gene, but not be dominant,
then I can't figure out how it would happen. Are there any other
biologists here with better knowledge of genetics to shed some light
on this?

JKR makes my brain hurt...lol

=)
Maddy