Wizards, Muggles, and Genetics (long)

[dungrollin]

No: HPFGUIDX 119731


> 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!!!) :)
<snip> 
> 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 replied:
> 
Snip> 
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.
> 
<snipping the biospeak>
> 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?


Dungrollin:
(Started writing this, then noticed Maddy's reply above, but can't 
be bothered to rewrite it)

I agree that the magic gene must be recessive and the non-magic gene 
dominant, otherwise at least one of Lily and Petunia's parents
would have been a witch or a wizard.

(A little clarification for those who never learned this, or, 
understandably, erased it from their memories:
You have two copies of each gene, of which you pass one to your 
offspring.  Thus, of the two copies that you have, one copy came 
from each of your parents.  

If the two copies are the same – e.g. Muggle/Muggle, then
you're a Muggle, similarly if they're magic/magic, then
you're a witch or a wizard. If they're different, then (aside
from complications like co-dominance that I won't get into) one
gene
is expressed and the other is not, so it depends on which gene is 
dominant. If the magic gene is dominant, then magic/Muggle people 
would be witches or wizards, if the Muggle gene is dominant then 
they'd be Muggles or squibs.  

So if the magic gene is dominant, then for Lily to have been a 
witch, at least one of her parents must have had at least one copy 
of the magic gene.  That would make one of her parents magic/muggle 
or magic/magic – ie, a witch or a wizard.  Geddit?)

Charme again:
<snip>
This could explain the appearance of Squibs in wizard families and 
while not common, we've already met 2 of them in the WW: Argus Filch 
and Arabella Figg. Other than the fact Filch and Arabella grew up in 
the wizard community, what *really* distinguishes them from 
muggleborns? With the same upbringing as Filch and Arabella, could a 
Muggle perform the same types of activities they do? It's 
conceivable a Muggle could. Muggle, BTW, is defined by LV in GoF 
as "not a wizard." Ok, so the only difference in definition between 
Muggle and Squib is what community (WW or Muggle) you were born in? 
Interesting those possibilities, hm?


But...
If Squibs are just muggles brought up in a magical household, how 
can they see dementors? (Thinking of Mrs. Figg's insistence in
the court.)  If there's no difference in the magical ability of 
purebloods and Muggle-borns, being brought up in a magical 
atmosphere can't make that much of a difference, can it?

Although there's the idea of magic genes acting as segregation 
distorters... Or the magic gene being mitochondrial, so only passed 
through the female line... Jumping magic genes... Not to mention, 
what exactly is the product of the magical gene? (If it is indeed 
only one gene.)  Magical proteins?  Magical hormones? Oh the 
possibilities are endless...  I somehow doubt that JKR has gone into 
too much detail.

What I'd like to know is what you call the non-magic offspring of
a witch/wizard and a Muggle.  Are they Squibs, or Muggles?

Ho hum.
Dungrollin