Anyone who has attended a high school biology conference on genetics understands the basics of dominant genetics and recessive alleles, which explain, among other things, how two brown-eyed parents can have a blue-eyed baby.
However, when you start talking about magical ability, things get more complicated.
That was the topic of a panel at Future Con, a “where science meets science fiction” convention, held this past weekend. In "Harry Potter and the Genetics of Magic," Duke University professor Eric Spana discussed the complexities of wizarding DNA.
Fans of "Harry Potter" know that, while two magical parents probably have magical children, that is not always the case. Occasionally, a completely magical union will result in a squib, or non-magical child (think poor Argus Filch, tasked with cleaning up all of Hogwarts without even a wand to help him). On the other hand, Hermione Granger, one of the greatest witches of all time, in my opinion, was born to two Muggle parents. Throughout the series, we learn that students like Seamus Finnigan had a magical father and a muggle father. So how the heck is magical ability transmitted?
According to a Live Science panel summary, Spana debated whether the magical ability was a recessive trait (much like the red hair of the Weasley family), which means that it is possible for an individual to carry the gene and potentially pass that gene on to offspring without expressing their traits. However, he ultimately decided it wasn't, thanks to one Rubeus Hagrid.
You see, Hagrid was born to a giant mother and a wizard father. This meant that Hagrid was born a wizard with only one copy of magical DNA in his blood (giants are not magical). Therefore, Spana concluded, magical ability must be a dominant trait.
If that's the case, how did Spana explain to children like Hermione who are the first in her family line with magical powers? A good old-fashioned genetic mutation, possibly occurring in a sperm or egg, or after the egg is fertilized. (Yes, don't you wish you had remembered more about AP Biology now?) As for squibs, Spana posited that parents could carry a mutation of the magic gene and pass it on to their children.
Science, man. It's quite magical.
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