wizarding genetics

[hp_fan_2008]

No: HPFGUIDX 183621

Catlady:
> I agree that the genetics of magic must involve quite a number of gene
> pairs, because simple Mendelian inheritance wouldn't account for
> wizarding folk having different amounts of innate magical power and
> being better at some forms of magic than others, and the magical
> alleles of these genes must be loose in the Muggle population or there
> wouldn't be Muggleborns.

HP Fan 2008:
Is there a genetic basis for magic? I think I can give an explanation
which nearly fits the full picture - the exception being Dean, who
isn't explicitly mentioned in the books as definitely having a wizard
father.

With the exception of Dean, all wizards/witches we know fall into one
of the following 2 categories:
1) Children to a witch mother - even if she is muggle-born herself.
2) Full muggle-borns - no known magical ancestry.

Here is the explanation: Ordinarily, a child gets the magical status
from the mother - hence the children of a witch mother will usually be
magical, and the children of a muggle mother will usually be a muggle.
There are exceptions in both directions - known as muggle-borns and
squibs. The reason there are more muggle-borns than squibs is the fact
that the wizard population is so small relative to the muggle population.

In addition to the question of having magic, there may also be the
question of the magic being strong enough to be noticeable. Some
"squibs" may actually be wizards or witches who actually are magical,
but the magic is so weak that it can't be used. Such people may also
be born to muggle families - I believe that the mother of the Creevey
brothers may be such, explaining why both brothers are wizards.

Catlady:
> I have tried, unsuccessfully but not very
> hard, to figure out how mixing these genes around could provide
> 'hybrid vigor', so that Muggleborns would usually be on the high side
> of the power range.

Are muggle-borns definitely typically better at magic? Not so clear.
Although Hermione is clearly near the top, but beyond that things
aren't so clear. Slughorn mentions that Lily was the best, but Lupin
refers to James and Sirius (both pure-blood) as the best in their
year. And see my comment above about Mrs. Creevey, who may have been
an extreemly-weak witch.

                                                    HP Fan 2008