Magic genetics

[kelleyaynn]

No: HPFGUIDX 146496

Kelleyaynn:

As several people have pointed out, Mendelian genetics isn't 
necessarily sufficient to explain how magic comes about. However, 
that doesn't mean that there is no Mendelian component to magic. 
Given that Muggle parents can have magic children, magic has to be 
recessive. That also explains why nearly all magical parents have 
magical children. Squibs, however present us with a quandry.

Genetics is actually very complicated. There are relatively few 
traits that exhibit strict Mendelian inheritance. That isn't because 
they are "rogue", or don't follow the laws of inheritance, it's 
because at the molecular level genetics is much more complicated. 
Genes have promoter and regulation sequences in the DNA that can 
impact whether a gene gets expressed and how strongly. Many traits 
result from the interaction of two or more genes. Some genes result 
in different traits, depending upon how they are transcribed and 
translated. Sometimes a completely different gene can affect whether 
another gene is expressed. 

I found it interesting that squibs are more common in pureblood 
families. That makes perfect sense genetically, as pureblood 
families tend to be rather inbred, and therefore harmful mutations 
are more likely to show up. 

I tend to view being a squib as similar to a learning disability. 
The ability may be there (hence the fact that we will see someone do 
magic late in life), but because of some other factor, it is 
difficult to nearly impossible for the individual to actually do 
magic. In this case the Mendelian genetics would still work, but 
something else is causing the lack of magical expression. 

So we can work our little Punnett Squares until we are batty, but we 
aren't going to be able to explain all aspects of magical expression 
by doing it. 

I just finished teaching genetics to my 7th graders (I am a 
biologist by training with a heavy emphasis on molecular genetics) 
and I always find it somewhat frustrating, for they always ask 
questions for which there are no simple answers. Too many people 
think Mendelian genetics explains everything. Actually, it explains 
very little. 

Kelleyaynn