"Blood" vs. genetics in the HP books (Was: Magic genetics)

[kelleyaynn]

No: HPFGUIDX 146542

> Finwitch:
> 
> How about combining both? I mean like the heritance of blood-type. 
The
> blood-type has *two* dominant allels: A and B; one recessive, 0. In
> addition there's the Rhesus-factor (and some others, but...).
> 
> As for how this applies to magic - well, maybe if the types A and B
> have magical form, it would explain the occasional squib (0-type). 
And
> I suppose that exhange between Magical A and Muggle A is a small 
one.
> 

Kelleyaynn:

But since both alleles for blood type (A and B) are dominant, they 
are expressed. So magic can't be a form of codominant alleles, since 
any muggle that had a dominant magic alleles would not be a muggle, 
but would be magical. 

Squibs are most easily explained genetically by the interference of 
a second gene, or perhaps a mutation in the promoter region of the 
magic gene, or some other reason that doesn't have to do directly 
with the magic gene (some other problem that interferes with the 
ability to do magic, kind of like a learning disability).

Finwitch:

> Also, if a mutation happens in reprocuctive cells, it would affect
> offspring, but not the parent - if elsewhere, it affects the 
parent if
> it happens in a cell where the gene functions...

Kelleyaynn:

Mutations occuring in any specific location in a genome are 
extremely rare (though mutations overall are not). So explaining 
magical children from muggles or squibs from magical parents by 
virtue of mutations in the germ line cells (the reproductive cells 
that give rise to eggs and sperm) is not really valid. They are too 
common to have happened that way, at least most of the time. 

I've said before that genetics is much more complicated than simple 
Mendelian rules. All the permutations of magical and non-magical 
people cannot be explained simply via Mendelian genetics. 

Kelleyaynn