genetics

[vheggie at yahoo.com]

No: HPFGUIDX 26769

Heh, I knew my degree (in genetics) would come in handy one day.  I 
didn't imagine it would be to debate the genetics of wizarding 
ability however....

I won't cut and paste all the previous debates - I'm a bit late in 
joining in, so I'll just throw in my own 2 knuts:

It's unlikely that magic ability is a single-gene condition:
1) Assume it's a recessive allele so mm = wizard and MM & Mm = muggle.
In order for two wizards to produce a squib a spontaneous mutation 
must occur which 'knocks out' the action of one of the parental 
genes.  This sort of mutation is INCREDIBLY rare, compared to the 
rates of hereditary diseases (which are also relatively uncommon).  
Off-hand, we're talking about not much more than one in a hundred 
thousand people suffereing from a spontaneous mutation of this sort.  
Most wizards probably wouldn't even have heard of a 'squib', or be 
aware of the possibility of having a 'squib', if this were the case.

2) Assume dominance so MM & Mm = wizard and mm = muggle.  No muggle 
parents could ever have wizards, unless a spontaneous mutation 
occured - see argument above - it is also a lot more infrequent for a 
spontaneous mutation to give INCREASED function to an allele (ie it's 
harder to 'make it work differently' than to 'break it') - people 
like Hermione would be one-in-a-million occurances - I think we can 
see from the text that muggle born wizards are a lot more common than 
that.

The more genetics is studied, the more we realise that things are 
never as simple as they seem.  The majority of intellectual, 
emotional, and even physiological characteristics are not the product 
of single genes.
It's clear that some people can be 'more magical' than others; 
Neville, IIRC worries that he was "not magical enough".  This 
suggests a polygenic condition; in this case, it would be perfectly 
possible to have both wizards and muggles with a complex set of genes 
for magical ability, allowing wizard parents to have squibs (who, 
after all, may well be able to do SOME magic - we don't know), and 
muggles to have wizards.

I imagine it being like musical ability - it's all very well having 
perfect pitch, but if you've poor coordination skills and lack the 
ability to regulate your breathing, you're never going to become a 
great pianist, or solo singer.