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Wizarding Genetics: More Complicated Than Mendel!

by Shinelikestars

Post date: July 30, 2005

 

Wizarding Genetics: More Complicated Than Mendel!

“A Squib is almost the opposite of a Muggle-born wizard: he or she is a non-magical person born to at least one magical parent. Squibs are rare; magic is a dominant and resilient gene.” – jkrowling.com

“Why are some people in the wizarding world (e.g., Harry) called 'half-blood' even though both their parents were magical?”

“The expressions 'pure-blood', 'half-blood' and 'Muggle-born' have been coined by people to whom these distinctions matter, and express their originators' prejudices. As far as somebody like Lucius Malfoy is concerned, for instance, a Muggle-born is as 'bad' as a Muggle. Therefore Harry would be considered only 'half' wizard, because of his mother's grandparents…. The Nazis used precisely the same warped logic as the Death Eaters. A single Jewish grandparent 'polluted' the blood, according to their propaganda.” (Therefore, Half-blood would be defined as having one Muggle grandparent.) – jkrowling.com

“How does a Muggle-born like Hermione develop magical abilities?”

“Nobody knows where magic comes from. It is like any other talent. Sometimes it seems to be inherited, but others are the only ones in their family who have the ability.” – Barnes and Noble interview, March 19, 1999

“How can two Muggles have a kid with magical powers?”

“It's the same as two black-haired people producing a redheaded child. Sometimes these things just happen, and no one really knows why!” – Online chat transcript, Scholastic.com, 3 February 2000

The Wizarding World

   J.K. Rowling is telling us several things about magical inheritance.  Magic is a “dominant and resilient gene”.  Yet, Muggle-borns are “the same as two black-haired people producing a redheaded child”, which implies that the gene for Muggle-borns is recessive.  (Hair color is more complicated than that, but that is the implication.) 

Harry’s class list suggests that the wizarding population is subdivided as follows.

  Muggle-borns    20%  
  Half-bloods 40%  
  Type 1: Muggle-born Parent  20%
  Type 2: Muggle Parent     10%
  Type 3: Muggle Grandparent 10%
Pure-bloods 40%  
  Slytherin 20%
  Other Houses 20%

    Since Muggle-borns are 20%, it follows that another 20% would be the children of Muggle-borns (people like Harry). That means the other Half-bloods are equally divided between literal “half-and-halves” (those like Dean and Seamus, who have one Muggle parent) and the children of those half-and-halves from the previous generation. There is only one type of Pure-blood – any wizard with two magical parents and four magical grandparents – but those in Slytherin are likely to share Voldemort’s racist agenda. This affects their choice of marriage partner and makes them more vulnerable to the genetic problems of in-breeding.

The Rules of Wizarding Genetics

   From canon and JKR herself, we can deduce quite a few rules of wizarding genetics:

  1. Magic is a "dominant and resilient" gene.
  2. Magic shows before age 11 in all magical people, with very rare exceptions.
  3. 40% of magical people are Pure-blood; they have no Muggle grandparents.
  4. None of the Pure-blood families are really "pure"; they disown Squibs.
  5. Pure-blood families are decreasing.
  6. 40% of magical people are Half-blood; with one Muggle parent or grandparent.  (We assume only 10% are actually half-and-half.)
  7. Half-bloods are magical, with rare exceptions (Seamus and Dean).
  8. 20% of witches and wizards are Muggle-born.
  9. Muggle-born inheritance of magic seems to be recessive.
  10. Muggle-borns may have non-magical siblings (Petunia).
  11. Squibs are the non-magical offspring of one or more magical parents.
  12. Squibs are rare (1 in 100 at the most, 1 in 1,000 at the least).
  13. Squibs have a higher chance of having magical children than Muggles do, even if they marry a Muggle (e.g., Mafalda Prewett, the missing Weasley cousin).
  14. Pure-bloods, Half-bloods, and Muggle-borns have magical children, regardless of the blood status of the other parent, with only rare exceptions.

   How can we explain this phenomenon from a genetic point of view?  Is magic inherited like hair color or eye color?  Is it a simple cross of two genes?  Or is it more complicated?

Mendelian Genetics

 

   First, we will quickly review a bit of biology (skip to the next paragraph if you know it, please). Remember, first of all, that everyone has 23 pairs of chromosomes (which have all of your genes on them) – 22 regular pairs which are called autosomes and two sex chromosomes. Everyone inherits 23 chromosomes from their mother and 23 from their father, which (except for the sex chromosomes) are basically identical. These 46 chromosomes are divided in half when forming sperm and eggs (gametes), only one chromosome from each pair going to a sperm or egg, so that each sperm or egg carries only 23 chromosomes. There is a 50% chance that the 1st chromosome in an egg will be from the maternal side and 50% chance that it will be from the paternal side.

   That’s all I want to say about biology, now to genetics. Everyone has two copies of each gene, but they may not be exactly identical, and these different forms of a single gene are called alleles. (I will use the word allele a lot, if it is confusing, simply substitute the word gene and it should make sense.) The brown/blue eye color gene has two alleles, brown (B) and blue (b). Brown is the dominant gene, blue is the recessive gene. So if a brown-eyed person had a child with a blue-eyed person, the Mendelian cross would look like this, where the mother is blue-eyed person, bb, on the side, and the father is the brown-eyed person, BB, at the top. Each letter represents one allele, and each parent has two alleles.

B

B

b

Bb

Bb

b

Bb

Bb

Or, BB x bb = children will all be Bb, having one B allele and one b allele

   The brown allele (B) is dominant, so because brown is dominant, all of those children will have brown eyes, even though they carry a blue allele. What happens if we cross someone with two blue alleles with someone with one brown, one blue?

B

b

b

Bb

bb

b

Bb

bb

Or, Bb x bb = ½ Bb and ½ bb

   One half of these children would have brown eyes, and the other half would have blue eyes. What if we took two people with one brown allele and one blue allele each?

  

B

b

B

BB

Bb

b

Bb

bb

Or, Bb x Bb = ¼ BB, ½ Bb, ¼ bb

  As you can see, three-fourths of the children will inherit a brown allele, which means their eyes, like their parents’ eyes, will be brown. One-fourth of the children, however, inherit two blue alleles, which means they will have blue eyes. This is statistically accurate – 25% will get two brown alleles, 50% will get one of each, and 25% will get two blue alleles. In crosses of more than one gene, there are still firm statistical ratios of which alleles go where, that most genes follow. The reason this is called Mendelian genetics is because Mendel was the man who first realized there were dominant and recessive genes by experimenting with pea plants.

Magical Mendelian Genetics

    Surprisingly, genetics for magical people are not actually very magical, but they are very unique. They do not follow traditional Mendelian genetics, which is why I’m writing this in the first place. If they followed Mendel exactly, it would be fairly easy to figure out. How do we know magical genetics don’t follow Mendel? Mendelian genetics cannot fit the rules in the HP world stated above.

    This is what Mendel’s rules would look like in the wizarding world. There is a gene called the magic gene, with two forms, M and N. There are magical people, with an M (magical) allele. There are Muggles who have an N (normal) allele. The M allele here is dominant over the N allele. Pure-bloods would have two copies of M, Half-bloods (the ones with one Muggle parent, also known as Half-and-half) would have one copy of each, MN, and Muggles would have two copies of N. That doesn’t leave much room for Muggle-borns or Squibs, but let’s pretend that Squibs also have two copies of N, like Muggles, and Muggle-borns have a copy of M, like magical people. The biggest problem right away is where the Muggle-borns got the M allele. If it is dominant, then they couldn’t have gotten it from their parents! There’s a slim chance that it was a new mutation, but the odds are not in favor of a new mutation happening so frequently that 20% of the magical population would have it. Besides, mutations almost always hurt people, not enhance them.

   For the sake of argument, let’s pretend that Muggle-borns have one M allele and one N allele, like Half-bloods. Purebloods have MM, Squibs are NN. These would be the results of several different crosses (Squibs are emphasized by an asterisk *):

M

N

M

MM

MN

M

MM

MN

Pure-blood x Half-blood

Pure-blood x Muggle-born

N

N

M

MN

MN

M

MN

MN

Pure-blood x Muggle

Pure-blood x Squib

M

N

M

MM

MN

N

MN

NN*

Half-blood x Muggle-born

Two Half-bloods

Two Muggle-borns

N

N

M

MN

MN

N

NN*

NN*

Half-blood x Muggle, Muggle-born x Muggle

Half-blood x Squib, Muggle-born x Squib

   Some of the time these crosses work and produce all-magical offspring, especially when it comes to Pure-blood crosses. Whenever it comes to Half-bloods or Muggle-borns, however, the crosses produce as many Squibs as magical children, and we know that Squibs are very rare (rule #12). We also know that magical people (no matter what their blood) have magical offspring almost exclusively (rule #14). We also know that Squibs have a better chance than a Muggle of having a magical child, and these Squibs do not, they are effectively Muggles (rule #13). This theory breaks several of our rules, as stated above. It also shows that the “Pure-blood” ideology may be right, that one Muggle grandparent taints the entire line, and we can be fairly certain that is not correct. We must find another theory.

The Magic Gene

 

    A better theory starts by comparing magical genetics to blood type. There are three alleles of the gene for blood type - A, B, and O. (I apologize if you already know this, skip ahead to the next paragraph.) Everyone has two alleles, giving possible combinations of AA, BB, OO, AO, BO, and AB. A and B are both enzymatically 'active' and are dominant, whereas O is not active and is recessive. So the four blood types then become A (AA and AO), B (BB and BO), AB (AB), and O (OO). The O gene is most common, followed by the A gene, then the B gene (although it is relatively rare). This gives percentages of blood type like so (in the US, and it is similar in most of Europe): O is 45%, A is 42%, B is 10% and AB is 3%.

   Now imagine that there are four alleles of the magic gene in the HP universe (instead of the two alleles mentioned above). There is M for magical, dominant; N for normal, or Muggle; r for magical, recessive; and o is a recessive mutation of M that can cause Squibs, seen primarily in Pure-blood families. Now assume that the dominance of these genes is as follows, from the most dominant to the least dominant:

M > N > r > o

    So then we have MM (Pure-blood), Mo (still Pure-blood with mutation), and oo (Squib). We also have NN (Muggle), Nr (Muggle), and rr (Muggle-borns, magical). To complicate things more, we have MN (half and half, usually magical), No (offspring of Muggle/Squib union), Mr (Half and half or Pure-blood, magical), and ro (offspring of Squib/Muggle union, magical). The reason ro children are magical is because r is dominant to the o allele, even if it is not dominant over the M or N alleles. Approximately 2% of the Muggle population carries one r allele, so 2% of these (0.04%) will marry another r-carrier. The chances that any one of their children will inherit the r allele from both parents are 1 in 4, so the odds of having a Muggle-born (rr) child are about 1 birth in 10,000. Not common, but common enough that there are a good number of Muggle-borns.

   Since the o allele is a mutation of M and it originated in the wizarding community, it is found almost exclusively in wizarding families. If two wizards carrying the mutant o allele marry, 1 in 4 of their children will be Squibs, 2 in 4 will be magical but will pass the mutant o to the next generation, and 1 in 4 will inherit two healthy M alleles. In case all of this sounds confusing, here are some examples:

  Vernon is more than likely NN. Petunia and Lily's parents were probably Nr, making Petunia NN or Nr (Muggle) and Lily rr (magical). Dudley is NN or possibly Nr (Muggle). Filch and Arabella Figg are both oo (Squibs), meaning their parents were likely both Mo. The Malfoys, Blacks, Potters, and Weasleys are all MM (Pure-blood magical), with perhaps an o here or there. Harry would be Mr (magical). Hermione is rr (magical), her parents are both Nr (Muggles). Seamus and Dean both are half-and-half, MN most likely.

M

M

r

Mr

Mr

r

Mr

Mr

Muggle-born x Pure-blood

M

N

r

Mr

Nr*

r

Mr

Nr*

Muggle-born x Half-blood

M

o

M

MM

Mo

N

MN

No*

Half-blood x Pure-blood mutation

N

N

M

MN

MN

N

NN*

NN*

Muggle-born x Muggle

   Wait, you say, how is that any better than the last theory? Half-bloods and Muggle-borns still are not able to have all magical children, Muggle-borns now have a recessive r gene, and the Half-bloods still carry that N gene! There are more Squibs than before, and we know that Squibs are rare.

The Half-Blood Quandary

    What do we do about the N allele in the Half-blood population? The solution to the Half-blood quandary is a second gene, a very special gene called Q. The Q gene is responsible for suppressing Muggle genes in each egg or sperm formed. Each egg or sperm (called a gamete) has ½ of each parent’s genes, so we have the possibilities of M, N, r, and o alleles being passed on, if a parent has that allele. Now then, if Q (an enzyme of some sort, made from the gene Q) were to stop the N gametes from ever becoming mature, allowing only M, r, and o to exist, then you would have an extremely high probability of having only magical offspring. (There is a recessive q that does not suppress genes, we will get to that!) Why doesn’t Q stop the o gametes as well? The Q gene cannot tell the difference between M and o, because o is simply an inactive mutation of M and looks similar enough to M that Q does not recognize it.

   If this Q gene keeps N from being passed on, why are there any Muggles left? Wouldn’t they all have died out by now? No, because the Q gene is only active in magical people. That part of the chromosome in Muggles is “covered up” by special proteins and cannot be uncovered, so the Q gene cannot do anything in a non-magical person. In a magical person, whether they are magical by inheriting the M allele or two r alleles, a chain-reaction begins in every cell of that person's body, which makes a lot of modifications (one of which is longer life). One of those modifications is "uncovering" the Q gene. So then the genes would be passed on like so:

M

M

r

Mr

Mr

r

Mr

Mr

Muggle-born x Pure-blood

r

r

M

Mr

Mr

N

 

 

Half-blood x Muggle-born

M

o

M

MM

Mo

N

 

 

Half-blood x Pure-blood mutation

N

N

r

Nr*

Nr*

r

Nr*

Nr*

Muggle-born x Muggle

N

N

M

MN

MN

N

 

 

Half-blood x Muggle

   Now the Half-blood N gene cannot be passed to the next generation, guaranteeing magical ability to all the children of Half-bloods. That fixes the Half-blood blood line. But the Muggle-borns are still turning out a very large number of Squibs.

The Muggle-Born Dilemma


   The solution to this Muggle-born dilemma is another job for the Q gene. Along with filtering out non-magical genes, the Q gene is responsible for changing the Muggle-born "r" allele (whether by itself or by turning on another gene). Why must the r allele be changed? So that Muggle-borns can pass on the magical trait as a dominant trait. So in a Muggle-born magical child, before they are even born, in every cell of their bodies, the Q gene produces enzymes that “cut” the r gene in different places and "stick" them back together again to look and act like the M allele. (This is cutting and gluing is called splicing, it is something that happens very often in our bodies, it is one of the reasons why we have so much “junk” DNA, and it is how we have so many different types of antibodies.) We could call this new, modified r allele the R allele, but since it looks and acts like M in every way, we will call it M as well and simplify things. So, keep in mind that even though Muggle-borns begin by being rr, they become MM, and pass on only M alleles. The modified r allele is in all respects identical to the M allele, and is, like the M allele, dominant to N. The Q gene then would cause Muggle-born pairs to make offspring like this:

M

M

r->M

MM

MM

r->M

MM

MM

Muggle-born x Pure-blood

M

N

r->M

MM

 

r->M

MM

 

Muggle-born x Half-blood

N

N

r->M

MN

MN

r->M

MN

MN

Muggle-born x Muggle

M

o

r->M

MM

Mo

r->M

MM

Mo

Muggle-born x Pure-blood mutation

   Muggle-borns now have the same benefits as Half-bloods, as far as their genes go. Now both of them can only pass on the dominant M allele, even if they themselves had an r allele to begin with. Now that changes things a little. Vernon is still NN. Petunia and Lily's parents were probably Nr, making Petunia NN or Nr (Muggle) and Lily rr (magical). Lily’s rr genes would have been changed to MM. Dudley is NN or possibly Nr (Muggle). Filch and Arabella Figg are both oo (Squibs), meaning their parents were likely both Mo. The Malfoys, Blacks, Potters, and Weasleys are all MM (Pure-blood magical), with perhaps an o allele here or there. Harry would be MM (magical), as his mother would have passed him an M gene instead of her r gene. Hermione is rr (magical), her parents are most likely both Nr (Muggles), but she will pass only M alleles to her children. Seamus and Dean both are half-and-half; MN most likely, but they will pass only M alleles to their offspring.

The Squib Enigma


   So where do Squibs come from? Isn't the Q gene supposed to prevent N from being passed on? Don’t forget about that nasty o mutation running through Pure-blood bloodlines. All oo wizards and witches are Squibs. That’s all well and good, but how could two half-and-halves have a Squib, or anyone else that wasn’t Pure-blooded? Well, there is a recessive q allele as well, that does not stop N from being passed on. (It does, however, still transform the Muggle-born r to M.)

   The Q and q alleles are fairly equally distributed – 25% of the population has two Q alleles, another 25% has two q alleles, and the remaining 50% have one Q and one q allele. A magical person only needs one Q allele to pass on only magical genes, and 75% of the magical community has at least one Q gene. However, 25% of the population is qq, and these individuals do not suppress non-magical genes, so they could very well pass an N allele! (Assuming they have one.) This N allele may be directly from the parent with qq, but it may also have been passed along a few generations before it showed up. If someone with an N allele (or an o) married another magical person, this wouldn't be too big a problem, unless they also were qq and also had an N (or an o) gene. If someone who was Moqq married someone who was MNqq, their child could very well be Noqq, a Squib. Some of the combinations that could produce Squibs (Squibs indicated with an asterisk *):

M

Nqq

M

MMqq

MNqq

Nqq

MNqq

NNqq*

Half-blood (qq) x Half-blood (qq)

M

o

M

MM

Mo

o

Mo

oo*

Pure-blood mutation x Pure-blood mutation

M

o

M

MM

Mo

Nqq

MNqq

Noqq*

Half-blood (qq) x Pure-blood mutation

M

o

N

MN

No*

N

MN

No*

Muggle x Pure-blood mutation

N

N

M

MN

MN

Nqq

NNqq*

NNqq*

Half-blood (qq) x Muggle


   Notice that with Muggles, it does not matter what their Q status is, because the Q gene is completely inactive in them. The Muggles could be qq, Qq, or QQ, it does not matter. Overall, marrying Muggles does increase your chances of having a Squib slightly, simply by introducing the N allele. However, the N allele is only passed on to the third generation if the parents both are qq. If the Muggle that marries in has a Q allele (or two), it actually slightly decreases the likelihood of having Squibs later, because more of the offspring would have a functional Q allele, and that will eventually “weed out” the N alleles (in their magical offspring anyway).

How Many Squibs Are There, Anyway?

   What is the likelihood of having a Squib? Squibs can be NN, No, or oo.

   The oo Squib. Approximately 6% of the total wizarding population has one o allele. It is never found among first generation Muggle-borns or Half-and-halves, but it occurs in 10% of Pure-bloods (4% of total wizarding population), just under 8% of Muggle-born offspring (1.5% of total wizarding population) and 5% of Half-and-half offspring (0.5% of total wizarding population). Assuming half of all Pure-bloods (20% of the total wizarding population) are prejudiced against others, 10% of these (2% of total wizarding population) carry the mutant o gene, and their insistence on marrying only another Pure-blood means that 10% of them (0.2% of total) will marry another o-carrier. In a marriage between two Mo wizards, a quarter of the children will be oo Squibs, so 1 in 2,000 wizard births will be Squibs born to prejudiced Pure-blood parents.

   The other 4% of the wizarding population (the other half of the Pure-bloods, 2% of the population, and then the second generation Muggle-borns and Half-and-halves, another 2% of the population) who carry the o allele are presumably willing to marry anyone, but in practice seven out of eight will marry another wizard. In most cases, the person they marry is not another Pure-blood, since many of the Pure-bloods have married each other. Of this 3.5% of the total population, the chances of marrying someone else who also carries the o allele is 4% (0.14% of the total). Again, a quarter of the children will be oo Squibs (0.035% of the total population, or 1 wizard birth in every 2,857).

   The No Squib. About 10% of wizards marry a Muggle, but none of these would be the prejudiced Pure-bloods, so 0.4% of wizarding marriages are between an o-carrier and a Muggle (NN).  Half of their children will be No Squibs, or 1 wizarding birth in every 500. This theory would explain very well the character of Thaddeus Thurkell who shows up in the "Famous Witches and Wizards" card set of the CoS video game. Thaddeus Thurkell "produced seven Squib sons and turned them all into hedgehogs in disgust”.

   The NN Squib. What about the offspring of half-and-halves that are qq, and therefore pass the N allele on to their offspring? First we will consider a marriage of two half-and-halves. We will assume half-and-halves are not too particular about whom they marry within the wizarding community. Approximately 10% of the wizarding community is actually half-and-half (remember, the other 30% of Half-bloods are children of Muggle-borns or other half-and-halves) and only a quarter of those carry qq. The odds of a qq (25%) half-and-half (10%) marrying another half-and-half (8.75%) that was also qq (25%) are 1 in 1,824, and only 1 in 4 of their children will end up NN, for an additional 1 Squibs per 7,000 births – next to none. Now we will consider a half-and-half with a Muggle. If a half-and-half (10%) that was qq (25%) happened to marry a Muggle (which we can assume does not happen much more often than 10% of the time), the odds of a Squib being born to that couple are 50%. So that could account for another 12 per 10,000.

   Notice that a Muggle-born (rr -> MM) who marries a Muggle (NN) never has a Squib child; however, Squib grandchildren are possible.

   Overall, we have a Squib birth rate of just fewer than 3 in 1,000. These are 0.85 in 1,000 oo Squibs, 2 in 1,000 No Squibs, and 0.14 in 1,000 NN Squibs, for a total of 2.99 Squibs in 1,000 wizarding births. If the wizarding community is about 30,000 people, there will be approximately 90 Squibs in all of the British Isles. As Ron said, “They’re really rare”, but they are not so rare that we couldn’t have met a few.

The Mafalda Prewett Mystery

   The likelihood of a Squib having a magical child is better than that of any two given Muggles producing a Muggle-born child, according to Rule #13 above, “Squibs have a higher chance of having magical children than Muggles do, even if they marry a Muggle (e.g., Mafalda Prewett).” How is that possible? Does the o allele become an M allele again? No – it’s simple arithmetic!

   For any two Muggles to have a magical child, the odds are 2% x 2% x ¼ = 0.01%, or 1 in 10,000. As I said previously, the order of dominance for the magic gene is M > N > r > o. Of all Squibs, 28% are oo, 67% are No, and 5% are NN. This is important, because NN Squibs are the exception to Rule #13. Now, if a Squib that is oo marries any Muggle, the odds of having a magical child are much higher than with a Muggle couple. How?

   If a Squib that is oo marries a Muggle that happens to be Nr (a 2% chance), and there is a 50% chance (the child will be either No or ro) of having a magical child, 1%, or, 1 in 100, children of Squib/Muggle marriages would be in fact magical. Squibs that are oo are 100 times more likely to have a magical child than any two Muggles are. No Squibs also have a higher chance of having a magical child than any two Muggles, 1 in 200. The NN Squib actually cannot have a magical child with a Muggle, because they can pass on only the N allele. Fortunately, fewer than 1 in 20 Squibs are NN. All of the ro magical children of oo or No Squibs and Nr Muggles would then become Mo, due to the Q gene modifications, and would re-enter the wizarding bloodline, carrying the o allele with them. We can show this here, where an asterisk * this time indicates a magical child:

N

r

o

No

ro*

o

No

ro*

Squib (oo) x Muggle (Nr)

N

r

N

NN

Nr

o

No

ro*

Squib (No) x Muggle (Nr)

N

r

N

NN

Nr

N

NN

Nr

Squib (NN) x Muggle (Nr)

   Remember that we stated earlier that Muggle-borns who are rr and marry Muggles (NN) do not have Squib children? It is very possible that a few Muggle-borns are actually ro children, descendants of Squibs a few generations earlier. These ro Muggle-borns then become Mo witches and wizards, and can very well pass the o gene on to further generations. So it is actually possible that a “Muggle-born” could have a Squib child, but they would have had to have a Squib ancestor at some point.

Wizarding Genetics, A History

   The reason why the M gene has not taken over the entire population of Britain yet is because for over 1,000 years, the Muggle and magical communities have been separated, passing genes back and forth occasionally, but mostly isolated. Approximately 90% of the wizarding population marries other wizards, effectively keeping the M allele within the magical community and the N allele out of the magical community. There is a very small proportion of the o allele in the Muggle population, because of Squibs leaving the magical community; however, the o allele is far more concentrated within the magical population. There are also far more r alleles than o alleles in the Muggle population, and the o allele in the Muggle population isn’t noticed at all; however, an No Muggle with an Nr Muggle could have an ro “Muggle-born” child.

   It has been argued that eventually the r allele would be weeded out of the Muggle population, if each rr child became MM and joined the wizarding community. However, that would take many, many, many generations, because for each rr child born, statistically, there are two Nr children born and one NN child; thus, the r allele continues in the Muggle population undetected until another rr child is born. Perhaps the r allele was more prevalent than 2% at one time. Perhaps that is how the magical community first started anyway – with Muggle-born witches and wizards, whose Q genes became activated and changed their r alleles to M alleles. These Muggle-borns began intermarrying when Muggles first began to fear magic and created the first Pure-blood families. The o mutation occurred sometime later, with the high population of Pure-blood families. Perhaps all of the Pure-blood families have their roots in Muggle-born ancestors. Magic had to start somewhere, after all.

A special thanks to Grace Has Victory, who did much of the dreadful number-crunching for me, and to Corned Bee, who kept finding the holes in my theory!

 

The Sugar Quill was created by Zsenya and Arabella. For questions, please send us an Owl!

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