[HPforGrownups] Re: Squibs have genes to do magic?

[Bart Lidofsky]

No: HPFGUIDX 146459

Steve wrote:
> So, let's ask ourselves from a more practical stand point if it is
> possible for a genius or a retarded person to occur in a family of
> people with normal intelligence? It would seem that both these event
> do occur.

Bart:
	Mental retardation is seldom genetic; FAR more often (when I worked 
with United Cerebral Palsy, the figure often given was 95% of the time), 
it is due to insufficient oxygen during gestation or birth. Genius, as 
well, seems to be more connected with the level of stimulus given in the 
early growing years than genetics, although many parents, in attempting 
to stimulate their children, actually create a stimulationally 
impovershed environment.

Steve:
> Another example, the children of two blonds are most likely to have
> blond hair, but that doesn't eleminate the possibility of some of
> their children having brown hair. 

Bart:
Actually, for the most part, it does. Blond is a recessive gene. If two 
parents have blond hair, it means they do not have the gene for brown 
hair. The only way a child of theirs can have brown hair is by mutation.

Consider, one magic gene pair, dominant. We will call the magic version 
W for Wizard/witch, and the non-magic M for muggle. Therefore, anybody 
with WW or WM will be a wizard. This means that there are 3 different 
kinds of wizard-witch marriages: WM-WM, WW-WM, and WW-WW. Now, let's 
look at the children:
WM-WM: WW, WM, WM, MM. One out of 4 will be a squib.
WW-WM: WW, WM, WM, WM. All will be magical.
WW-WW: WW, WW, WW, WW. All will be magical.

Bringing in Magic/Muggle marriages, we have WW-MM, and WM-MM.
WW-MM: All children will be WM.
WM-MM: WM, WM, MM, MM: half the children will be squibs.

Therefore, if magic were a single, dominant gene, there would be a good 
proportion of squibs being born.

However, if it were a recessive gene, then ALL wizards would be WW, but 
unless a wizard marries a WM muggle (WM's would not be magical), all the 
children would be squibs. On the other hand, if a WM muggle marries 
another WM muggle, one out of 4 children would be magical.

None of this fits in with JKR's statements. Therefore, one must either 
assume that magic is not based on a single gene pair, or that there are 
other forces at work. Now, for example, it could be that there is a 
non-random factor in magical matings; that it is biologically recessive, 
but that the M genes make the sperm and egg much more likely to combine. 
We have not been told what happens if two squibs marry, although one 
might assume that it would not be that an uncommon occurrance 
(considering the relative isolation of squibs).

Now, if there are two gene pairs involved, it gets much more 
complicated. However, given the Statute of Secrecy, we don't even know 
how people from the Wizarding World commonly meet and marry muggles anyway.

Unfortunately, the most likely theory is that JKR never really thought 
it through.

	Bart