Huh. Not quite...

[conuly]

Reading JKR's site, she has some new stuff about squibs up (told you that Mrs. Figg never really saw the dementors, and couldn't if she'd been there). Among other things, she says that squibs are so rare because "magic is a dominant and resilient gene".

Well, I'm not going to ask what "resilient gene" means. However, let's take the statement that magic is governed by a single dominant gene at face value.

We know that Dean has brothers and sisters, JKR's site said that somewhere. They're apparently only half-siblings (and presumably on his mother's side), but that doesn't matter to this entry. We also know that his story was cut out of the HP books, his dad (unbeknownst to him) was a wizard. Okay.

Now, Dean's siblings don't go to Hogwarts. That means that Dean's dad only had one Magic gene (M) and another gene that says no-magic (m). His mother presumably has no copies of the magic gene, because she's a muggle (mm).

So, Dean's genes are also Mm. That's the only possible outcome. Now, let's say that Dean gets on with somebody else who has one muggle and one magic parent. That person would also have to have the combination Mm, unless of course there was a random mutation (such as the one which presumably is behind Hermione's existence).

It's not hard to put together a simple chart:

x  M    m

M  MM   Mm

m  Mm   mm

So, Dean's kids would have a 25% chance of not being magical, despite having two wizarding parents.

It's not altogether unlikely that he'd marry a muggle - after all, he grew up with muggles, sees them every time he visits home, is part of that world as well. I'm not making another chart, let's just say that now there'd be a 50% chance of his kids being non-magical.

Of course, you say, there's still the purebloods! Surely squibs are only the non-magical children from pureblood families!

First off, we don't know that. Secondly, that argument doesn't hold water. While it's certainly possible for a family to pass along a recessive gene for generations before it appears, it's not that likely. And we know that there aren't very many pureblood families left. More inbreeding, more chances of squib-gene carriers to meet and have kids, more squibs. You'd expect to see something like a quarter of all children born to wizard parents being squibs.

Well, of course, maybe they are, and people just kinda hush it up, send them out to be adopted, thus making true squibs (nonmagical kids raised in the wizarding world) rare.

But...

Look at Neville. Until recently, he didn't seem to have much magical talent, his family thought he was "all-squib for ages" and that he wasn't quite magical enough to get into Hogwarts. By contrast, some people (Dumbledore, Voldy) seem to be excessively powerful, doing things "with a wand I'd never seen before". It would seem that there's a range of magical ability from muggle/squib to powerfulwizard.

A range of magical ability... hm... kinda like there's a range of skin color from "black" to "burns in moonlight" or a range of heights from "dwarf" to "giant"? But these things are multi-gene traits. They're not governed by a single recessive gene (and, to an extent, they are also influenced by environment. Tallness is a recessive trait (found in many genes), but your height can be affected by your diet in childhood and whether or not you slept with a nightlight). It seems logical that magic is similarly governed by multiple genes. Hermione's parents might be partly magical without knowing it - not enough to get into Hogwarts, but enough to pass on the right combination of genes to their daughter.

But this only works for multi-gened-traits.

Comments

[adiva_calandia]

*applauds your nerdiness* Actually, it's double nerdiness, since you've got the HP and the genetics. I think magic would definitely be multi-gened, just judging by the fact that there's a range of talents.

Have you ever had conversations about how hobbits may have evolved? *blushes* Cuz I have. . . .

[conuly]

I don't like LotR, so no, haven't.

And I'm not that nerdy. I just liked this section of bio, even the first time 'round.

[adiva_calandia]

Heh heh heh. . . .

I have. *looks sheepish*

[marveen.livejournal.com]

Our consensus was that hobbits were likely a three-way cross between Elves, Dwarves and Men. After all, Men and Elves can crossbreed (cf. Elrond Halfelven), so why not Dwarves and Men?

Basic template--Men
Half-height--Dwarves
Beardless--Elves
Hairy feet--mutation, because the Vanil alone know where that came from

(And on magical inheritance--why does it have to work like "ordinary" genes? Magical spells aren't subject to conservation of matter, after all, or Malfoy would have been a ferret the size of a German Shepherd--uh, I mean Alsation.)

Re: I have. *looks sheepish*

[conuly]

Magical spells aren't subject to conservation of matter, after all, or Malfoy would have been a ferret the size of a German Shepherd--uh, I mean Alsation.

Unless he was an exceptionally dense ferret.

Even Rita Skeeter could've been a very dense beetle utilizing a levitation charm.

Re: I have. *looks sheepish*

[adiva_calandia]

Hmm. . . I'm not sure where they originally came from -- dwarves maybe -- but I always thought they had just evolved into a smaller size, pointed ears for hearing noises. . . . not sure where the hairy feet came in. I think Tolkien just threw that in to be confusing.

[eofs.livejournal.com]

Dean's brothers and sisters aren't wizards/witches because they don't share his father - they're half brothers and sisters.

[conuly]

You sure? Could you linky me?

[eofs.livejournal.com]

I am sure, for the same reason that you're sure about his father ;0)

3rd paragraph. (http://www.jkrowling.com/textonly/extrastuff_view.cfm?id=2)

[deceptica]

I'm curious, how and why can sleeping with a nightlight affect your growth?

[conuly]

Your pituitary gland works best 1. when you're sleeping and 2. if it's dark, or so said my first three bio teachers.

[feathered.livejournal.com]

Whoo. So that explains why I am shorter than everyone else in my family! My fear-of-dark is to blame! And my insomnia!

Dunno if it's true, but it's a very cool idea.

[bridgetester.livejournal.com]

It would seem that there's a range of magical ability from muggle/squib to powerfulwizard.

I read somewhere... I don't remember where that she has a list of all the pupils of Hogwarts (and other major characters) with their house, level of magical powers, etc. There was a picture of part of the list too.

If magic is governed by a single gene, then the pureblood families should be more powerful. However, they would also be more sickly from the inbreeding.

[conuly]

If magic is governed by a single gene, then the pureblood families should be more powerful.

Not so. Think about it. If magic were governed by a single recessive gene, then pureblood families would (probably) tend to have fewer squibs - but there probably would not be a real variation in degree of magical power.

If magic were governed by a single dominant gene, pureblood families, again, would likely have fewer squibs, but, again, there probably wouldn't be any real variation in degree of magical power.

There's also "semi-recessive" and "co-dominant" genes. That's what's involved when a cross between a red lily and a white lily gives a pink lily or one that's red and white together.

If magic were governed by a single semi-recessive or co-dominant (the two terms are not synonymous) gene, you *would* see variations in magical power, and magical families probably would be stronger than non-magical ones... but I doubt JKR considered that possibility.

And, at any rate, I still think that pureblood families have a better chance of being "stronger" with a multi-gened trait - there's more variation, which means there's more of an opportunity for *anybody* to be stronger or weaker.

[adiva_calandia]

*applauds your nerdiness* Actually, it's double nerdiness, since you've got the HP and the genetics. I think magic would definitely be multi-gened, just judging by the fact that there's a range of talents.

Have you ever had conversations about how hobbits may have evolved? *blushes* Cuz I have. . . .

[conuly]

I don't like LotR, so no, haven't.

And I'm not that nerdy. I just liked this section of bio, even the first time 'round.

I have. *looks sheepish*

[marveen.livejournal.com]

Our consensus was that hobbits were likely a three-way cross between Elves, Dwarves and Men. After all, Men and Elves can crossbreed (cf. Elrond Halfelven), so why not Dwarves and Men?

Basic template--Men
Half-height--Dwarves
Beardless--Elves
Hairy feet--mutation, because the Vanil alone know where that came from

(And on magical inheritance--why does it have to work like "ordinary" genes? Magical spells aren't subject to conservation of matter, after all, or Malfoy would have been a ferret the size of a German Shepherd--uh, I mean Alsation.)

[eofs.livejournal.com]

Dean's brothers and sisters aren't wizards/witches because they don't share his father - they're half brothers and sisters.

[conuly]

You sure? Could you linky me?

[deceptica]

I'm curious, how and why can sleeping with a nightlight affect your growth?

[conuly]

Your pituitary gland works best 1. when you're sleeping and 2. if it's dark, or so said my first three bio teachers.

[girls-are-weird.livejournal.com]

hey. great ideas. i was wondering about that myself so i googled "resilient gene" and coincidentally found this post ^^;;;

it's a good theory, but then again, rowling wasn't going for multi-gened traits. she doesn't care about magic being in a "range." after all, she did say "there is no question of not being ‘magical enough’; you are either magical or you are not." i wish she wouldn't say those things ("dominant & resilient") as she obviously doesn't go too deep into it, but then we do and we get stuck. lol. not to mention a gene being dominant & resilient is just not possible. (BTW, i'm not sure but from what i gather, resilient means something along the lines of traits skipping generations. but dominant genes can't do that).

anyway, i liked your theory very much. it's not often that i find HP fans who get into these things as much as i do ^_^

[bridgetester.livejournal.com]

It would seem that there's a range of magical ability from muggle/squib to powerfulwizard.

I read somewhere... I don't remember where that she has a list of all the pupils of Hogwarts (and other major characters) with their house, level of magical powers, etc. There was a picture of part of the list too.

If magic is governed by a single gene, then the pureblood families should be more powerful. However, they would also be more sickly from the inbreeding.

[conuly]

If magic is governed by a single gene, then the pureblood families should be more powerful.

Not so. Think about it. If magic were governed by a single recessive gene, then pureblood families would (probably) tend to have fewer squibs - but there probably would not be a real variation in degree of magical power.

If magic were governed by a single dominant gene, pureblood families, again, would likely have fewer squibs, but, again, there probably wouldn't be any real variation in degree of magical power.

There's also "semi-recessive" and "co-dominant" genes. That's what's involved when a cross between a red lily and a white lily gives a pink lily or one that's red and white together.

If magic were governed by a single semi-recessive or co-dominant (the two terms are not synonymous) gene, you *would* see variations in magical power, and magical families probably would be stronger than non-magical ones... but I doubt JKR considered that possibility.

And, at any rate, I still think that pureblood families have a better chance of being "stronger" with a multi-gened trait - there's more variation, which means there's more of an opportunity for *anybody* to be stronger or weaker.

[girls-are-weird.livejournal.com]

hey. great ideas. i was wondering about that myself so i googled "resilient gene" and coincidentally found this post ^^;;;

it's a good theory, but then again, rowling wasn't going for multi-gened traits. she doesn't care about magic being in a "range." after all, she did say "there is no question of not being ‘magical enough’; you are either magical or you are not." i wish she wouldn't say those things ("dominant & resilient") as she obviously doesn't go too deep into it, but then we do and we get stuck. lol. not to mention a gene being dominant & resilient is just not possible. (BTW, i'm not sure but from what i gather, resilient means something along the lines of traits skipping generations. but dominant genes can't do that).

anyway, i liked your theory very much. it's not often that i find HP fans who get into these things as much as i do ^_^