Mudbloods, Half-Bloods, Pure Bloods, and Genetics

[Andrew]

No: HPFGUIDX 88749

--- In HPforGrownups at yahoogroups.com, "drjuliehoward" 
<drjuliehoward at y...> wrote:
> I have a strange question that I know has been touched upon in 
some 
> ways by past posts.  It has been 17 years since I had genetics so 
my 
> knowledge is very rusty.  How is magic passed down genetically?  
> 1.  It cannot be Dominant, given that there are squibs and 
mudbloods.
> 2.  It cannot be complete recessive, given that there are 
halfbloods.
> 3.  At what point is a wizard a pureblood?  
> 4.  Is magic genetic at all?

Basic high school genetics here, which could account for all of 
this. There would have to be two chromosomes attached to this trait. 
One dominant magic charactaristic that would explain why a wizard 
almost always has a magical child. And one recessive to explain why 
there may suddenly appear a magical person in a totally muggle 
family. I'll attempt to draw a simple picture here for you.

w=wizard recessive
W=wizard dominant
m=muggle recessive    
M=muggle dominant                     
                       
                         
                   M    w
              M  0 MM 0 Mw 0
              w  0 Mw 0 ww 0
1   In one case,MM, the child will be totally muggle.
2   In the second case, Mw, the child will be a muggle, but will 
carry the wizard chromosome (which in a later generation, if paired 
with another recessive w gene, it will create on possible wizard)
3   In the last case, ww, the child is magical. 
4   1/4 chances of a magical child.

There may also be a magical dominant trait which when paired with a 
muggle dominant trait, it will over power the muggle trait.
                  M     w
             W 0 WM 0 Ww 0
             w 0 Mw 0 ww 0
1   The case, WM, wizard overpowers muggle creating a wizard child 
with a muggle trait, which may evenutally lead to a squib in a later 
generation.
2   The case, Ww, leaves a magical child. Possible problem with 
squib in later generation, if paired with a M dominant trait.
3   The case, Mw, creates a muggle(squib), with a recessive wizard 
gene.
4   The last case, ww, creates a wizard.

This seems highly simplified but is illustrated to the best of my 
ability. Perhaps there is a biology professor/teacher out there that 
can provide another explanation.

Andrew