Another reason to love the Harry Potter books

Wow. I'm totally surprised at the response I got from my Lurker Day post. I expected maybe one third the response. I'm also flattered at some of the comments. In fact, I think I may address a few of them sometime over the weekend if I get time. In the meantime, if you're a lurker and haven't de-lurked, please go here and let me know you're reading.

On to other topics...

Via Stupid Evil Bastard, I've found another reason to love the Harry Potter books. British geneticists Jeffrey M. Craig, Renee Dow, and Mary Ann Aitken examined the chromosomal basis of being a wizard or a muggle, suggesting that wizarding ability is inherited in a Mendelian fashion as a recessive. Last month, they even got their idea published as a Letter to Nature. They speculated:

Wizards or witches can be of any race, and may be the offspring of a wizard and a witch, the offspring of two muggles ('muggle-born'), or of mixed ancestry ('half-blood').

This suggests that wizarding ability is inherited in a mendelian fashion, with the wizard allele (W) being recessive to the muggle allele (M). According to this hypothesis, all wizards and witches therefore have two copies of the wizard allele (WW). Harry's friends Ron Weasley and Neville Longbottom and his arch-enemy Draco Malfoy are 'pure-blood' wizards: WW with WW ancestors for generations back. Harry's friend Hermione is a powerful muggle-born witch (WW with WM parents). Their classmate Seamus is a half-blood wizard, the son of a witch and a muggle (WW with one WW and one WM parent). Harry (WW with WW parents) is not considered a pure-blood, as his mother was muggle-born.

There may even be examples of incomplete penetrance (Neville has poor wizarding skills) and possible mutations or questionable paternity: Filch, the caretaker, is a 'squib', someone born into a wizarding family but with no wizarding powers of their own.

We believe that, with the use of these examples, the concepts of mendelian genetics can be introduced to children as young as five, and then built on by gradually introducing specific terms such as 'gene' and 'allele', and relating these to chromosomes and DNA. At every stage, the children's familiarity with the Harry Potter characters can be used as a hook to engage them in discussing concepts of heredity and genetics.

I like it. Too bad I missed the original letter, which Panda's Thumb pointed out when it was originally published. (I think the reason I missed this one is because it came out while I was on vacation and I never quite caught up on the journals that piled up in my absence, ending up just filing many of them away mostly unread.) In any case, although I know a lot about genetics, I'm not a geneticist. Even so, I realize that this proposed explanation is probably too simplistic. Fortunately for my ability to blog on this without seeming a month and a half out of date, another group of scientists, not to be outdone, agree. They fired off a retort that was published in Nature last week:

Following Craig and colleagues' analogy, Hermione, as a muggle-born witch, must have WM parents. However, as Rowling fans could point out, Hermione's parents were muggle dentists who lack any family history of wizarding. It's true, of course, that chance may not have thrown up a witch or wizard for many generations, or that any who did have magical powers may have kept them secret to avoid a witch hunt.

What about Neville's apparently poor wizarding skills? These cannot be explained by incomplete penetrance, as Craig and colleagues suggest. In incomplete penetrance, individuals either display the trait or not: they do not display an intermediate degree of the trait. Poor wizarding skills might be indicative of variable expressivity of an allele. However, both variable expressivity and incomplete penetrance are associated with dominant alleles. If the wizarding allele were dominant, rather than recessive as suggested, wizarding children such as Hermione could not be born to non-wizarding parents.

Neville's clumsiness may, perhaps, be an individual characteristic unrelated to his potential powers. However, it is not possible, from the evidence presented so far, to conclude that wizarding is a heritable trait.

Hmmmm. They have a point there. However, if wizarding abilities are not somehow heritable, then what determines who is a wizard and a muggle? Or should I just realize that it's only fiction and stop contemplating the question?

Of course not! What fun would that be? In any case, the discussion in the comment section after the original Panda's Thumb article has some entertaining speculation:

Wizardy is clearly a quantitative, multigenic trait with variable expressivity and incomplete penetrance. I wouldn’t discount a role for epigenetic effects either.

Or:

Possibly the magic ability is only partly inherited. One explanation for squibs and muggle-born wizards/witches would be that the allele(s) for magic are fairly common in the population, but that they are expressed only when they are triggered by some external factor. This factor would have to act sometime in the early years (wizards and witches develop their abilities slowly up to around age eleven, and there is no mention in the books of someone gaining magical powers as an adult.) This factor could simply be exposure to magic, or to some microorganism that is endemic to the wizarding community. Muggle-born wizards/witches could come from accidental exposure to either of these. If it is a microorganism, squibs could be explained by immunity from an earlier infection by a related organism. It would be an exciting topic for a research project!

Personally, I favor the latter explanation, but it could be simply because I understand that explanation better than the former. (My memories of my genetics classes are getting hazier, the further out from graduate school I get.) Regardless of the obviously tongue-in-cheek nature of this little exchange, I like the concept of using Harry Potter to teach young children some very basic concepts of genetics and inheritence described in the first letter. Given the sorry state of biology education in this country, any reasonable gimmick should help. Heck, it might even work. Yes, the concept of wizarding skills doesn't quite fall into a concept based on Mendelian inheritance, but it's close enough to provide a "teachable moment." Besides, the second group of scientists were probably just expressing sour grapes because they didn't think of the idea first. I do note, however, that they cleverly managed to get their names on a Letter to Nature, just like the first group of scientists. Having any publication in Nature, even just a letter, is a an addition to one's CV that many scientists would kill for. I know I'd have to think about it if someone told me that all I'd have to do is to kill someone to get a first author paper in Nature. Just kidding.

Barely.

Of course, there is yet another upside to this idea, if it ever caught on. Teaching genetics also implies implies the acceptance of evolution and could even provide an "in" to introducing basic concepts of evolution. As SEB and Clive both point out, that's another reason for the Christian right to hate Harry Potter. Not only would they accuse J. K. Rowling of indoctrinating children into witchcraft, but they could accuse her of something many of them probably view as even worse: introducing them to concepts of evolution.