who are you callin' a homozygote?
Sep. 6th, 2003 12:15 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
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mollymoon asked. I wrote this up a while ago, to get my own thoughts in order. Yeah, I know the wizarding world doesn't obey the laws of biology. But if it did...
The Genetics of Harry Potter
Introduction
Before we get started, here's a quick overview of basic genetics: Each gene determines one physical trait. A gene comes in two parts, called alleles, which are usually represented by letters of the alphabet. In some genes, one allele is dominant (represented by a capital letter) and the other is recessive (represented by a lower case letter). If the dominant allele is present, the trait it determines always shows up, whether the other allele is the dominant one or the recessive one. A recessive trait only appears if both alleles are recessive.
An individual who has two of the same allele is called homozygous. An individual who has two different alleles from the same gene is called heterozygous.
The physical traits of an individual are called the individual's phenotype. The actual alleles that underlie these physical traits are called the individual's genotype.
During reproduction, the genes of each parent split into their component alleles, and one allele from each parent is contributed to the offspring, making one whole gene. It's random which allele is contributed.
It's really more complicated than this, of course, but that's all you need to know to start with.
One Gene, Complete Dominance
In this theory, magical ability is determined by a single gene; its two alleles are the dominant M (Muggle) and the recessive m (wizard). There are two possible phenotypes (Muggle or wizard), but three possible genotypes:
Two wizard parents (homozygous by definition) will always produce wizard
offspring:
Two homozygous Muggle parents will always produce homozygous Muggle offspring:
A homozygous Muggle and a homozygous wizard will also produce all Muggle offspring, but they will all be heterozygous:
If one of these heterozygous Muggles marries a wizard, their offspring will have a 50% chance of being a heterozygous Muggle, and a 50% chance of being a wizard. Wizards with such parents are "half-bloods", like Seamus Finnegan. We can see that the elder Mr. Finnegan must have been a heterozygous individual — in other words, he must have had at least two wizard ancestors somewhere in his family tree (assuming no sibling incest). We can also see that Seamus has exactly the same genotype (mm) as any other wizard — genetically, his magic is just as "pure" as Draco Malfoy's:
Now, the children of two heterozygous Muggles have a 25% chance of being a homozygous Muggle, a 50% chance of being a heterozygous Muggle, and a 25% chance of being a wizard. That one-in-four shot is a "Muggle-born", like Hermione. Again, we see that Hermione's magical genotype is aboslutely identical to that of a "pure-blood" wizard:
But there's a problem with this theory. If magic is a simple recessive trait, two wizard parents should always produce wizard offspring. What about Squibs? Mutation could account for some, but there could be another explanation: incomplete dominance of the Muggle allele.
One Gene, Incomplete Dominance
If this is the case, we still have two alleles: MM (Muggle) and MW (wizard). But neither one is completely dominant over the other. There are still three genotypes, and now there are three phenotypes as well:
In incomplete dominance, we would expect the heterozygous genotype to be found in individuals with some Muggle and some wizard traits. There is now no such thing as a heterozygous Muggle.
Homozygous wizards still produce all wizard offspring:
Homozygous Muggles still produce all Muggle offspring:
A homozygous Muggle and a homozygous wizard still produce all heterozygous offspring, but unlike in the complete dominance theory, they will all be wizards, though we will expect them to have weaker magic than their wizard parent:
A homozygous Muggle and a heterozygous wizard may produce either Muggle or (half-)wizard offspring, but there is only a 25% chance that their child will be a wizard. Under this theory, wizards who marry Muggles are running a greater risk that their children will be Muggles too:
The child of two heterozygous wizards has a 25% chance of being a homozygous wizard, a 50% chance of being a heterozygous wizard, and a 25% chance of being a homozygous Muggle (in other words, a Squib):
Now we see the value of keeping the magical bloodline "pure". Wizards with Muggle ancestry run the risk of having Squib children, whereas pure-blood wizards do not. If we accept this theory, we're forced to admit that Voldemort and his followers are on the right track: intermarriage is harmful to the wizarding community, and pure-bloods are more talented than half-bloods.
But there's a problem with the incomplete dominance theory too. If all Muggles are homozygous, how do we account for the existence of Muggle-born wizards? We might theorize that apparent "Muggle-borns" are actually children of heterozygous individuals whose genotype includes the magical allele, but whose actual magical ability is negligible. (In order to calculate the degree of dominance of one allele over the other, we'd have to know the genotypes of the individual's ancestors, and how long ago the last intermarriage took place.) If this is so, then we would expect the parents of Muggle-borns to have some magical talent — perhaps the occasional prophetic dream, or the ability to see ghosts — but I see no support for this in canon.
And there's another problem, too: we know several wizards who must be heterozygous under this theory, and though we would expect them to be weak, some are exceptionally talented: Hermione is one, as is Voldemort himself. Perhaps this can be attributed to high intelligence, ambition, and proper training (this is probably how Voldemort justifies his own power to himself), but is it really reasonable to accept that individuals with such a weak phenotype that they may as well be Muggles can produce a prodigy like Hermione?
It seems that neither complete nor incomplete dominance fully accounts for
what we see in canon. But there's another possibility.
Multiple Genes
Many different types of magic are taught at Hogwarts, and the students show differing degrees of ...predisposition (as Snape might say) to one subject or another. Most tellingly, some magical skills are spoken of as entirely or partly inborn (Divination and Metamorphmagic, for example). This suggests that magical ability is not determined by one single gene, but many.
This really opens up the possibilities. There may be a gene (or multiple genes) for each ability, plus a single wizard gene that triggers the expression of the magical alleles. There will be countless genotypes and phenotypes that are all lumped together under the general category "wizard". This also allows for both Muggle-born wizards and Squibs.
In this case, the trait of being a Squib would have a separate gene. Let's say the alleles are a recessive s (Squib) and a dominant S (non-Squib). A homozygous wizard may be a carrier of the recessive Squib trait without even realizing it. If two carriers marry, 25% of their offspring will not carry the recessive Squib allele, 50% will carry the allele but not express it in their phenotype, and 25% will in fact be Squibs:
This gets even more interesting when you look at intermarriages between wizards and Muggles (assuming that magical and Squib genes are not linked in such a way that Muggles can't carry the Squib alleles). For example: With a homozygous wizard parent and a heterozygous Muggle parent who are both heterozygous for the Squib trait, 12.5% of the offspring will be non-carrier Muggles, 25% will be carrier Muggles heterozygous for the Squib trait, 12.5% will be carrier Muggles homozygous for the Squib trait, 12.5% will be non-carrier wizards, 25% will be carrier wizards, and 12.5% will be true Squibs (genotype mmss). Phenotypically, it will be impossible to distinguish between the Muggle children (MmSS, MmSs, and Mmss) and the true Squib children (mmss); two recessive Squib alleles will have no effect on individuals who already had the dominant Muggle allele in the first place:
A number of fans have theorized that Squibs may have latent magical abilities, or a different kind of magic all their own. The multiple gene theory allows for this: perhaps the Squib gene overrides some magical genes, but not others.
Dudley's Decision
We don't have enough information about the different types of magical ability and how they correlate to work out what the full "magical genome" would look like. But here's an example of how it might work: let's assume the existence of a Divination gene (dominant D [Seer] and recessive d [non-Seer]) and a Metamorphmagic gene (dominant P [non-Metamorphmagus] and recessive p [Metamorphmagus]).
Their son Harry has the phenotype "wizard, non-Squib, non-Seer, non-Metamorphmagus", so his genotype must be either mmSSddPp or mmSSddPP. Given his parentage, the former had a 25% chance of occurring, and the latter a 12.5% chance. (It will be impossible to tell which genotype Harry has until he has children with a woman whose genotype is known. Stay tuned, folks...)
Now, Lily is Muggle-born. One or both of her parents must have carried the dominant Divination allele (D), but not expressed it in their phenotype due to the overriding presence of the dominant Muggle allele (M). (It's also possible that the D allele was partially expressed through occasional prophetic dreams or somesuch, if the M allele is incompletely dominant.)
Let's say Mr. and Mrs. Evans both had the genotype MmSSDdPp. Focusing on the Muggle and Divination genes (so that the chart doesn't get too out of hand), we see that each of their children stood a 25% chance of being a wizard, and an 18.75% chance of being a wizard with Divination talent; also, a 75% chance of being a Muggle, and a 56.25% chance of being a Muggle
who carries the dominant Divination allele.
Let's say Lily's sister Petunia has the genotype MmDd. And let's say Petunia's husband Vernon has the genotype MMDD. As Vernon is a "pure-blooded" Muggle (could he be any other kind?), their son Dudley cannot be a wizard. However, he will certainly carry the dominant Divination gene. Without the recessive wizard gene, can Divination manifest itself in his phenotype (shades of Clyde Bruckman)? Does it make a difference if he has one recessive wizard allele? Only time will tell...
In any case, Dudley may want to be picky in his choice of partners. If he is heterozygous for the wizard gene, and happens to marry another heterozygous Muggle, he stands a 25% chance of giving Vernon and Petunia a grandchild who prophesizes the gory demise of everyone he meets.
Toujours Pur
So, now what can we say about Voldemort's theory of wizard genetics? Are pure-bloods any better than half-bloods or Muggle-borns? The multiple gene theory suggests not. If Muggles can carry magical genes (as the very existence of Muggle-borns implies), then a wizard of mixed blood should be just as likely to have a powerful genotype as any pure-blood. Any wizard may unknowingly carry the recessive Squib allele — and obsessive inbreeding will only exacerbate the problem.
The conclusion is inescapable: Voldemort's beliefs have their basis not in fact, but in delusion. But it's not too much of a stretch to imagine an aspiring young Death Eater poring over genetics textbooks in an effort to justify his resentment through science.
On a somewhat similar note,mollymoon also brought up the question of whether lycanthropy can be passed from parent to child (presumably only mother to child, since it's an acquired illness and not genetic). To know that, we'd have to figure out how it's passed... Saliva apparently carries the virus(?) -- perhaps blood does too. Any thoughts?
mollymoon asked. I wrote this up a while ago, to get my own thoughts in order. Yeah, I know the wizarding world doesn't obey the laws of biology. But if it did...The Genetics of Harry Potter
Introduction
Before we get started, here's a quick overview of basic genetics: Each gene determines one physical trait. A gene comes in two parts, called alleles, which are usually represented by letters of the alphabet. In some genes, one allele is dominant (represented by a capital letter) and the other is recessive (represented by a lower case letter). If the dominant allele is present, the trait it determines always shows up, whether the other allele is the dominant one or the recessive one. A recessive trait only appears if both alleles are recessive.
An individual who has two of the same allele is called homozygous. An individual who has two different alleles from the same gene is called heterozygous.
The physical traits of an individual are called the individual's phenotype. The actual alleles that underlie these physical traits are called the individual's genotype.
During reproduction, the genes of each parent split into their component alleles, and one allele from each parent is contributed to the offspring, making one whole gene. It's random which allele is contributed.
It's really more complicated than this, of course, but that's all you need to know to start with.
One Gene, Complete Dominance
In this theory, magical ability is determined by a single gene; its two alleles are the dominant M (Muggle) and the recessive m (wizard). There are two possible phenotypes (Muggle or wizard), but three possible genotypes:
|
|
|
| MM | homozygous | Muggle |
| Mm | heterozygous | Muggle |
| mm | homozygous | wizard |
Two wizard parents (homozygous by definition) will always produce wizard
offspring:
| m | m | |
| m | mm | mm |
| m | mm | mm |
Two homozygous Muggle parents will always produce homozygous Muggle offspring:
| M | M | |
| M | MM | MM |
| M | MM | MM |
A homozygous Muggle and a homozygous wizard will also produce all Muggle offspring, but they will all be heterozygous:
| M | M | |
| m | Mm | Mm |
| m | Mm | Mm |
If one of these heterozygous Muggles marries a wizard, their offspring will have a 50% chance of being a heterozygous Muggle, and a 50% chance of being a wizard. Wizards with such parents are "half-bloods", like Seamus Finnegan. We can see that the elder Mr. Finnegan must have been a heterozygous individual — in other words, he must have had at least two wizard ancestors somewhere in his family tree (assuming no sibling incest). We can also see that Seamus has exactly the same genotype (mm) as any other wizard — genetically, his magic is just as "pure" as Draco Malfoy's:
| M | m | |
| m | Mm | mm |
| m | Mm | mm |
Now, the children of two heterozygous Muggles have a 25% chance of being a homozygous Muggle, a 50% chance of being a heterozygous Muggle, and a 25% chance of being a wizard. That one-in-four shot is a "Muggle-born", like Hermione. Again, we see that Hermione's magical genotype is aboslutely identical to that of a "pure-blood" wizard:
| M | m | |
| M | MM | Mm |
| m | Mm | mm |
But there's a problem with this theory. If magic is a simple recessive trait, two wizard parents should always produce wizard offspring. What about Squibs? Mutation could account for some, but there could be another explanation: incomplete dominance of the Muggle allele.
One Gene, Incomplete Dominance
If this is the case, we still have two alleles: MM (Muggle) and MW (wizard). But neither one is completely dominant over the other. There are still three genotypes, and now there are three phenotypes as well:
|
|
|
| MMMM | homozygous | Muggle |
| MMMW | heterozygous | (half-)wizard |
| MWMW | homozygous | wizard |
In incomplete dominance, we would expect the heterozygous genotype to be found in individuals with some Muggle and some wizard traits. There is now no such thing as a heterozygous Muggle.
Homozygous wizards still produce all wizard offspring:
| MW | MW | |
| MW | MWMW | MWMW |
| MW | MWMW | MWMW |
Homozygous Muggles still produce all Muggle offspring:
| MM | MM | |
| MM | MMMM | MMMM |
| MM | MMMM | MMMM |
A homozygous Muggle and a homozygous wizard still produce all heterozygous offspring, but unlike in the complete dominance theory, they will all be wizards, though we will expect them to have weaker magic than their wizard parent:
| MM | MM | |
| MW | MMMW | MMMW |
| MW | MMMW | MMMW |
A homozygous Muggle and a heterozygous wizard may produce either Muggle or (half-)wizard offspring, but there is only a 25% chance that their child will be a wizard. Under this theory, wizards who marry Muggles are running a greater risk that their children will be Muggles too:
| MM | MM | |
| MM | MMMM | MMMM |
| MW | MMMM | MMMW |
The child of two heterozygous wizards has a 25% chance of being a homozygous wizard, a 50% chance of being a heterozygous wizard, and a 25% chance of being a homozygous Muggle (in other words, a Squib):
| MM | MW | |
| MM | MMMM | MMMW |
| MW | MMMW | MWMW |
Now we see the value of keeping the magical bloodline "pure". Wizards with Muggle ancestry run the risk of having Squib children, whereas pure-blood wizards do not. If we accept this theory, we're forced to admit that Voldemort and his followers are on the right track: intermarriage is harmful to the wizarding community, and pure-bloods are more talented than half-bloods.
But there's a problem with the incomplete dominance theory too. If all Muggles are homozygous, how do we account for the existence of Muggle-born wizards? We might theorize that apparent "Muggle-borns" are actually children of heterozygous individuals whose genotype includes the magical allele, but whose actual magical ability is negligible. (In order to calculate the degree of dominance of one allele over the other, we'd have to know the genotypes of the individual's ancestors, and how long ago the last intermarriage took place.) If this is so, then we would expect the parents of Muggle-borns to have some magical talent — perhaps the occasional prophetic dream, or the ability to see ghosts — but I see no support for this in canon.
And there's another problem, too: we know several wizards who must be heterozygous under this theory, and though we would expect them to be weak, some are exceptionally talented: Hermione is one, as is Voldemort himself. Perhaps this can be attributed to high intelligence, ambition, and proper training (this is probably how Voldemort justifies his own power to himself), but is it really reasonable to accept that individuals with such a weak phenotype that they may as well be Muggles can produce a prodigy like Hermione?
It seems that neither complete nor incomplete dominance fully accounts for
what we see in canon. But there's another possibility.
Multiple Genes
Many different types of magic are taught at Hogwarts, and the students show differing degrees of ...predisposition (as Snape might say) to one subject or another. Most tellingly, some magical skills are spoken of as entirely or partly inborn (Divination and Metamorphmagic, for example). This suggests that magical ability is not determined by one single gene, but many.
This really opens up the possibilities. There may be a gene (or multiple genes) for each ability, plus a single wizard gene that triggers the expression of the magical alleles. There will be countless genotypes and phenotypes that are all lumped together under the general category "wizard". This also allows for both Muggle-born wizards and Squibs.
In this case, the trait of being a Squib would have a separate gene. Let's say the alleles are a recessive s (Squib) and a dominant S (non-Squib). A homozygous wizard may be a carrier of the recessive Squib trait without even realizing it. If two carriers marry, 25% of their offspring will not carry the recessive Squib allele, 50% will carry the allele but not express it in their phenotype, and 25% will in fact be Squibs:
| mS | mS | ms | ms | |
| mS | mmSS | mmSS | mmSs | mmSs |
| mS | mmSS | mmSS | mmSs | mmSs |
| ms | mmSs | mmSs | mmss | mmss |
| ms | mmSs | mmSs | mmss | mmss |
This gets even more interesting when you look at intermarriages between wizards and Muggles (assuming that magical and Squib genes are not linked in such a way that Muggles can't carry the Squib alleles). For example: With a homozygous wizard parent and a heterozygous Muggle parent who are both heterozygous for the Squib trait, 12.5% of the offspring will be non-carrier Muggles, 25% will be carrier Muggles heterozygous for the Squib trait, 12.5% will be carrier Muggles homozygous for the Squib trait, 12.5% will be non-carrier wizards, 25% will be carrier wizards, and 12.5% will be true Squibs (genotype mmss). Phenotypically, it will be impossible to distinguish between the Muggle children (MmSS, MmSs, and Mmss) and the true Squib children (mmss); two recessive Squib alleles will have no effect on individuals who already had the dominant Muggle allele in the first place:
| MS | mS | Ms | ms | |
| mS | MmSS | mmSS | MmSs | mmSs |
| mS | MmSS | mmSS | MmSs | mmSs |
| ms | MmSs | mmSs | Mmss | mmss |
| ms | MmSs | mmSs | Mmss | mmss |
A number of fans have theorized that Squibs may have latent magical abilities, or a different kind of magic all their own. The multiple gene theory allows for this: perhaps the Squib gene overrides some magical genes, but not others.
Dudley's Decision
We don't have enough information about the different types of magical ability and how they correlate to work out what the full "magical genome" would look like. But here's an example of how it might work: let's assume the existence of a Divination gene (dominant D [Seer] and recessive d [non-Seer]) and a Metamorphmagic gene (dominant P [non-Metamorphmagus] and recessive p [Metamorphmagus]).
Let's use as our example parents James (genotype mmSSddPp, phenotype "wizard, non-Squib, non-Seer, non-Metamorphmagus") and Lily (genotype mmSSDdPp, phenotype "wizard, non-Squib, Seer, non-Metamorphmagus"). Their offspring will all be wizards and none Squibs, and will have the Divination and Seer genes in the following assortment:
|
||||
| dP | dP | dp | dp | |
| DP | DdPP | DdPP | DdPp | DdPp |
| dP | ddPP | ddPP | ddPp | ddPp |
| Dp | DdPp | DdPp | Ddpp | Ddpp |
| dp | ddPp | ddPp | ddpp | ddpp |
Their son Harry has the phenotype "wizard, non-Squib, non-Seer, non-Metamorphmagus", so his genotype must be either mmSSddPp or mmSSddPP. Given his parentage, the former had a 25% chance of occurring, and the latter a 12.5% chance. (It will be impossible to tell which genotype Harry has until he has children with a woman whose genotype is known. Stay tuned, folks...)
Now, Lily is Muggle-born. One or both of her parents must have carried the dominant Divination allele (D), but not expressed it in their phenotype due to the overriding presence of the dominant Muggle allele (M). (It's also possible that the D allele was partially expressed through occasional prophetic dreams or somesuch, if the M allele is incompletely dominant.)
Let's say Mr. and Mrs. Evans both had the genotype MmSSDdPp. Focusing on the Muggle and Divination genes (so that the chart doesn't get too out of hand), we see that each of their children stood a 25% chance of being a wizard, and an 18.75% chance of being a wizard with Divination talent; also, a 75% chance of being a Muggle, and a 56.25% chance of being a Muggle
who carries the dominant Divination allele.
|
||||
| MD | Md | mD | md | |
| MD | MMDD | MMDd | MmDD | MmDd |
| Md | MMDd | MMdd | MmDd | Mmdd |
| mD | MmDD | MmDd | mmDD | mmDd |
| md | MmDd | Mmdd | mmDd | mmdd |
Let's say Lily's sister Petunia has the genotype MmDd. And let's say Petunia's husband Vernon has the genotype MMDD. As Vernon is a "pure-blooded" Muggle (could he be any other kind?), their son Dudley cannot be a wizard. However, he will certainly carry the dominant Divination gene. Without the recessive wizard gene, can Divination manifest itself in his phenotype (shades of Clyde Bruckman)? Does it make a difference if he has one recessive wizard allele? Only time will tell...
In any case, Dudley may want to be picky in his choice of partners. If he is heterozygous for the wizard gene, and happens to marry another heterozygous Muggle, he stands a 25% chance of giving Vernon and Petunia a grandchild who prophesizes the gory demise of everyone he meets.
|
||||
| MD | Md | mD | md | |
| MD | MMDD | MMDd | MmDD | MmDd |
| MD | MMDD | MMDd | MmDD | MmDd |
| MD | MMDD | MMDd | MmDD | MmDd |
| MD | MNDD | MMDd | MmDD | MmDd |
Toujours Pur
So, now what can we say about Voldemort's theory of wizard genetics? Are pure-bloods any better than half-bloods or Muggle-borns? The multiple gene theory suggests not. If Muggles can carry magical genes (as the very existence of Muggle-borns implies), then a wizard of mixed blood should be just as likely to have a powerful genotype as any pure-blood. Any wizard may unknowingly carry the recessive Squib allele — and obsessive inbreeding will only exacerbate the problem.
The conclusion is inescapable: Voldemort's beliefs have their basis not in fact, but in delusion. But it's not too much of a stretch to imagine an aspiring young Death Eater poring over genetics textbooks in an effort to justify his resentment through science.
On a somewhat similar note,
mollymoon also brought up the question of whether lycanthropy can be passed from parent to child (presumably only mother to child, since it's an acquired illness and not genetic). To know that, we'd have to figure out how it's passed... Saliva apparently carries the virus(?) -- perhaps blood does too. Any thoughts?
![[identity profile]](https://www.dreamwidth.org/img/silk/identity/openid.png){kind=small}
no subject
Date: 2003-09-06 01:29 am (UTC)no subject
Date: 2003-09-06 03:27 am (UTC)I've seen other explanations of genetics and how it could work with magic, but none as good as this.
I don't really know about lycanthropy. I think because of the fact that the wizarding world doesn't work by biological rules (or if it does, I doubt JKR will explain) it's unlikely we'll find out.
We also don't know exactly what happens when a werewolf bites another. Is it just the saliva? Or the fact that it comes into contact with the blood? Or is it just completely magical?
I have no idea whether it could be passed on or not. All I've succeeded in doing is confusing myself!
Kel
no subject
Date: 2003-09-06 12:09 pm (UTC)Can I use this in a story? Not neccesarily explain it, but use it for a background? Oh, and the Lily being a Seer thing too! (Or at least carrying a Seer gene.) Please?
An Awed Faelori
no subject
Date: 2003-09-06 12:16 pm (UTC)Any wizard may unknowingly carry the recessive Squib allele — and obsessive inbreeding will only exacerbate the problem.
And not opnly this problem: disease does not seem to be much of an issue in the magical world, but over time Wizard endogamy ought to have resulted in a higher rate or genetic disorders than in the regular population. (Rowling may not care; my guess is that magical medicine simply covers up many of the resulting problems).
no subject
Date: 2003-09-07 08:22 pm (UTC)Don't tempt me...!
the Divination allele seems relatively rare, but the M allele much more common, given that all four Marauders possessed it
By metamorphmagic I meant the innate transformative abilities that Nymphadora Tonks was born with, not the capacity to become an Animagus, which is a learned skill. However, this does point out the fact that some of the magical alleles are completely dominant, while others are not... Where T determines innate Transfiguration skill, if James found the Animagus transformation very easy, he may have T+T+, but since Peter found it very difficult, he could have been T+T-.
no subject
Date: 2003-09-07 10:21 pm (UTC)Oh, drat. I'm a complete idiot to forget about that!
no subject
Date: 2003-09-08 07:13 am (UTC)I definately agree that it has to be particular magical subtraits in addition to possessing the magical gene itself that makes a wizard/witch who they are in terms of power. Education can only go so far, eventually you just have to be talented in one area in order to excell.
Now for the lycanthropy issue.
When I was talking to you about Homo Lupus (a werewolf such as Remus is) vs Canis Sapiens (the wise wolf) I don't know if I mentioned one very important aspect of that theory -- the "mother" of the Canis Sapiens would be a regular wolf.
Let's use Remus as an example throughout this. Remus is transformed during a full moon and comes across a female wolf in heat. He mates with her and bites her during the process. She is now (1) Pregnant and (2) a carrier of the werewolf disease. My plot bunny says that when these pups were born, they would be Canis Sapiens -- wise, perhaps even talking wolves for the whole of the month until the full moon, when they transform into humans. They would age as wolves and perhaps be nearly unknown to the wizarding world... somewhere along the lines of myth/slander that Tom Riddles uses against Hagrid in CoS ("...raising werewolf cubs under the bed.")
Now, when you first think of those talking puppies, it sounds damn cute... but when you ponder in the aging and life that these creatures are doomed too, its horrifying. It is for me, the plot bunny that will not die.
As far as other ways to pass on the disease, I would agree that only if the mother is infected could the disease pass to a human baby.
Forgive any incoherantness, its still early in the morning for me.
no subject
Date: 2003-09-08 11:31 am (UTC)no subject
Date: 2003-09-08 11:44 am (UTC)The idea was born out of a desire to give my young Remus a penpal and star-crossed lover. It was originally suppose to happen in the story I'm writing now, Return to Sender, but new canon from OotP changed the focus of that story slightly. Other factors needed in that plot bunny have pushed it into the next novella, Deliver Us from Evil.
That will give me time to brush up on my photoshop and HTML skills as well, as that aspect of the story, the penpal romance, is an homage to one of my favorite series, "Griffin and Sabine". If you've never read those little books, they are basically the correspondence between two people. The catch is that you get to open the letters within the book. Each character is somewhat of an artist and designs their own envelope, paper etc. Its all very beautiful and gives the reader a connection to the characters that really lasts the test of time.
no subject
Date: 2003-09-08 12:23 pm (UTC)no subject
Date: 2003-09-08 12:34 pm (UTC)JKR had said in an interview prior to OotP release, that when she created this world, she decided that Muggles diseases, such as cancer, didn't effect wizards, or were totally curable in their world. Meaning of course that there must be other afflictions that prey on this population. Otherwise, one would assume that Wizards would out populate Muggles.
Lycanthropy and vampirism could both be such diseases for the Wizarding community. Its an interesting jump in thought to look at how our modern mythology has evolved a war between werewolves and vampires... What if such a thing existed in the WW as well? Perhaps lycanthropy was first a "made" disease... we know that werewolves are unusual because they speficially target humans... Maybe lycanthropy was a potion gone wrong and instead of transforming the drinker into a vampire killing machine... well, that's enough supposition for the day. And probably enough abuse of elipses as well.
*waits for the release of Underworld (http://www.sonypictures.com/movies/underworld/) as only a reformed Goth can*
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Date: 2003-09-08 11:21 pm (UTC)I don't think that either the Seer trait or Metamorphmagus trait are single gene traits, though. It'd be pretty weird if the Blacks were carriers of the Metamorphmagus trait, but none of the ones we know mainfested it, considering they're part of a relatively endogamous group. And then for it to manifest in an out-cross like Tonks, well it seems unlikely.
I don't have a specific argument for why Seer can't be a simple genetic trait, but I don't think it is. As Faelori mentioned, we did some work on Seer as a complex trait resulting from a combination of several neural traits, which are not necessarily correlated, so different balances can result in different flavors of Seers. Most or all of these traits are effected by environmental factors, as well as the complex genetics that direct brain development.
For example, maybe there's a kernel of truth to the "seventh son" thing for Seers. The womb's chemical environment changes in seim-predictable ways with succesive pregnancies: perhaps later pregnancies are more likely to produce Seers.
i want to get some of my neurodevelopment references (currently out on loan) back before I write it all up, but I'll do it fairly soon either way, and post a link.
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Date: 2003-09-08 11:28 pm (UTC)Looked more closely at some of the comments that have gone up since I first read. The T+T- incomplete dominant gene sounds like a good idea, and maybe Metamorphmagi are T+T+, combined with another trait? Plus of course, mmS*. Complicated, being a metamorphmagus :)
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Date: 2003-09-15 09:45 am (UTC)This is a good idea. I picked the Metamorphmagus and Divination traits essentially at random, and I admit they may not have been good examples. It did occur to me that it seems strange for Tonks, an out-cross, to have such an unusual trait. But then again, that's why I pointed out at the start that the wizarding world does _not_ follow the laws of biology! I mean, I bought that "Science of Harry Potter" book, but I know perfectly well that, as far as canon is concerned, it's full o' crap. :)
About the only thing in HP that makes sense with our scientific view of the world is the psychology, and even _that_ is sometimes debatable, and depends very much on which character you're discussing.
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Date: 2003-09-14 01:43 am (UTC)If voldemort wants wizards to be pure-bred, its like animal breeders who breed so they can register animals in a closed registry. That is you breed pure-bred-Siamese to pure-bred-Siamese and you always get pure-bred Siamese (pure wizard x pure wizard = pure wizards). You don't breed 2 alley cats who "look" Siamese together (you could get non-Siamese by virtue of hidden recessive coat types, hidden spotting genes, genes affecting body types etc.) (mudblood x mudblood = mudbloods and squibs). You don't breed pure-bred-Siamese to pure-bred-maincoon, as you'll end up with black and tabby "mutts" etc. (wizard x muggle = squib and mudblood; mudblood x muggle = mudbloods and squibs).
In small populations, an otherwise "rare" allele (good or bad) can become very common very quickly. Lots of examples of this in real life. To stick with cats: Manx cats on the Isle of Man for example. Although there are many in humans also, very often seen in small island communities or mountain villages cut off from the rest of the world by terrain.
Inbreeding doesn't have to exacerbate the problem, there are inbred, healthy populations (although its something like for every successful inbred line of animals, 10 other inbred lines failed). If the squib allele is a simple recessive as you suggest, it is actually easy to breed it out of a population, even while inbreeding (actually it can breed it out faster that way). The commonly thought of way to do this is to prevent an affected individual or a carrier from breeding. But if the unwanted gene is common, doing this will cause the population to become more inbred and you get rid of one mutation only to have other more serious one pop up (look what happened to the Basenji dog breed!). (Hmm, I wonder what would be a worse genetic mutation then the squib allele in that case?) What you need to do is to use carriers to breed to noncarriers, and then replace the carrier parents with non-carrier offspring who maintain the genetic diversity from the parents but not the unwanted allele.
cont. next post due to length
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Date: 2003-09-14 10:48 pm (UTC)Yes, I know. Where did I say otherwise?
I'm not quite sure what to make of your point about Siamese cats; my understanding is that cat genetics is very complicated. However, the issue of a cat that "looks" Siamese doesn't seem relevant here, because we're not talking about appearance, we're talking about specific, discrete magical abilities. If I can perform magic, I'm a wizard. What other possible definition of "wizard" could there be?
Your argument is nebulous to me. Are you saying that muggleborns ARE less likely to be powerful in canon (which relies on absence of evidence), or are you saying that by my hypothesis, they SHOULD BE less likely to be powerful (which you have not adequately explained)?
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Date: 2003-09-15 05:01 am (UTC)I left out the word ‘powerful’, I was referring to your saying: “If Muggles can carry magical genes … then a wizard of mixed blood should be just as likely to have a powerful genotype as any pure-blood.”
I'm not quite sure what to make of your point about Siamese cats; my understanding is that cat genetics is very complicated.
Genetics of ANY species is complicated! Wizard/human genetics would be no ‘easier’ than that of cats or rats or fruit flies.
However, the issue of a cat that "looks" Siamese doesn't seem relevant here, because we're not talking about appearance, we're talking about specific, discrete magical abilities. If I can perform magic, I'm a wizard. What other possible definition of "wizard" could there be?
There is no species that is genetically “magical” we know of for me to have used as an example. Therefor I used genetics of appearance (colour, coat). That’s generally easier for people to grasp first before say environmentally influenced health genetics which is harder to “see”, or in this case hidden magical ability.
Personally I think making each talent a simple dominant or recessive gene is oversimplified. There are no simple mutations for ability in calculus, painting, playing the piano, etc.. There are some genes that seem to influence abilities in a general sense- but this is not specific traits and not single genes. Thus with magic, divination ability for example may be influenced by tens of different genes in addition to environmental influences. Some genes may affect muggles to a degree while others may not… for example, a talented muggle gardener may owe some of that inborn talent to the same genes that make a wizard good with herbology. And that’s not even touching on the other magical talents. All together there could be hundreds of involved genes, and they may not all be considered strictly magical. Much in the way colour-point (the dark nose, feet, ears and tail of a Siamese) is a distinguishing feature of the Siamese breed- but it can also be present in other breeds, like ragdolls, but it doesn’t make that cat a Siamese.
Just as you suggest several genes are needed to make a powerful wizard, we know that several genes (for colour, coat, body stucture etc.) are needed to make a show-quality Siamese (I'm thinking here powerful = show quality; wizard = siamese for compareson). While those Siamese-related genes may exist in a feral population of cats in my alley, I would be very surprised to see ALL of them coincidently come together in one kitten, resulting in a cat that looked like a show quality Siamese, despite its background. Likewise, the idea of a powerful wizard from 2 muggles although * possible * would be very unlikely.
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Date: 2003-09-15 05:05 am (UTC)Your hypothesis makes it so that muggle borns would be less likely to be powerful.
Not that they can’t be, just less likely. We know there are very fewer wizards then muggles, & that wizards tend to intermarry which is a form of inbreeding. we don’t need JKR to say muggleborns are more or less powerful. We just need to know if its genetic (seems to be), if its a simple recessive, polygenetic etc., & the number of wizards to muggles. Figuring out the frequencies & chances of being a powerful wizard (if that is determined polygenetically) is like figuring out the frequency/risks of genetic disease in a population.
If its just one gene- powerfulness could be determined by other factors- eg the same ones that would work in muggles, plus enviroment. EG, a gene gives on talent at working with plants, makes a muggle a good gardener, or a wizard a good herbologist. In such a case, I’d say powerfulness of the wizard is no more/less likely then talent/IQ in a muggle.
We don’t have information in canon on how many muggle born wizards occur in the muggle population- but that muggles tend to be fearful & not-understanding of wizards says to me that most don’t know one (don’t have on in the family). Also the size of the Wizarding world seems small compared to that of muggles- Hogwarts teaches all of the pure-blood, mudblood & muggle-born wizards in what all of the U.K.? & how many schools are needed to teach all of the muggle children in the UK. A lot! So we don’t have very many wizards popping out of muggles. Which means the allele(s) that make one magical must be rare in muggle population.
If just one gene makes one a moderately powerful wizard, then although few wizards are produced, they’d at least be of average magical ability. However, if you add in even a few more magical genes that work together, then your odds of getting a wizard from muggles is not only rare, but they are more likely to have only 1 or 2 of the several genes needed- making them weak wizards. The likelihood of getting ALL the genes to make them very powerful is very slim. This is what I was getting at with the cats.
At least when wizards are inbreeding, they know that they all have the wizard gene- what they may worry about is the frequency of the squib allele (if that is a recessive genetic “disease”), as well as what the magical abilities are in the lineages- since they can * See * the magical abilities in the family members, they can thus select for the traits. Breeding FOR traits changes the allelic frequencies, making the more “popular” more prevalent (and any associated genes, which may be negative as well, thus resulting in inbred populations having rare diseases suddenly become common).
Muggles would not be able to see divination or transfiguration ability when its hidden in their family trees due to lack of (or rare pairing up of) the wizard gene. They essentially are randomly breeding, keeping the allelic frequency unchanged. So That frequency must be pretty low based on the size of the muggle & wizard populations I interpret from reading (Is there anywhere were JKR has given actual numbers for the populations? If so, then if we just looked at magical ability, assuming that it’s a single gene trait (set aside powerfulness from other multiple gene traits) we could mathematically figure out the frequency of the allele. Of course, I’m assuming, given that this is random breeding based on we have heard about muggles marrying wizards. However if this is rarely done, if looked down on in both cultures, then muggles aren’t really randomly breeding, they are slowly breeding the wizard genes out of their population (that is, if when there is a muggle born, they are most likely to marry another wizard, rather then marry back into muggle society, this act slowly reduces the frequency of the wizard alleles in the muggle population & thus in time it becomes more & more rare to get muggle-borns)
continued post
Date: 2003-09-14 01:43 am (UTC)Theoretically, they could obsessively inbreed and build up a sizable, healthy population, if it was carefully controlled. It would require genetic testing of all wizards and arranged marriages based on those genetics, and prevention of certain people from breeding (or permitting them to only have 1 child to "replace" themselves and then could no longer breed)- some kind of ministry ordered sterilization. Of course, that’s all from animal breeding. Applying this to people opens that whole can of worms about eugenics (well it already has been opened, but not really discussed in detail in the books), human rights, procreation for the 'state' rather then as a result of 2 people being in love etc.
Another possibility is that alleles that are "good" in one dose are "bad" in double doses. THIS would more likely cause irreparable problems in an inbred population. For example- what if there is no Squib gene? What if divination is dominant and good in 1 dose (maybe there are modifier genes at other loci that determine how powerful one's divination abilities can be) but 2 copies of the gene causes squibness? To breed out the Squib-casing mutation, you must breed out divination ability. To preserve divination ability, you must accept squibness in an inbred population (or they might required some genetic testing to prevent 2 people with the D gene from having children together).
That could also happen with recessives. Lets say squibness is recessive as you said. But carrying the squib gene makes you immune to lycanthropy. Thus being a carrier of the squibness is a good thing for you (but not so much for the child you have with another carrier who gets that 25% chance of being a squib). That could put squibs in an interesting social position in locations where werewolves are a big problem. Marrying a Squib might be desirable to a family who does not carry the squib gene as it would result in children who are all wizards and all carry the squib gene and thus are all immune to lycanthropy
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Date: 2004-10-13 04:18 pm (UTC)*fangirls you madly*
The crop of Muggleborn students we see at Hogwarts is something that always interested me (seems disproportionately high, all things considered,) but as I'm hopeless with science, I could never quite put together how it might be tied to genetics.
*files this away for future consultation*
Brilliant, brilliant, brilliant.