Bloodline genetics!
So I'd have done this sooner or later as annexe to anything NejiHina I'd do, but it's good to have this done. So... yeah! Basic bloodline genetics for dummies! (Addresses both the Sharingan and tbe Byakugan)
I. Vocabulary and generalities
II. First scenario: the gene is recessive
III. Second scenario: the gene is dominant.
IV. Other ways to "increase" the odds
V. Reviving the clan! Possible scenarios.
VI. Naruto genetics according to the anime! \.^_^.\ Or why you shouldn't all take this too seriously.
I still say that Kishimoto probably didn't bother with genetics. ;)
I'll kill anyone by the way who decides to use this to argue that Neji and Hinata for example will be forced into an arranged marriage in CANON as a result. ^^ Before you die though, I'll be sure to drill into your head that "This is a shounen manga so there will be no forced relationships," hear? Anything that happens will be on a strictly voluntary basis. Besides, if Hinata or Neji are forced into Anything, you can expect the Main Character (tm) to come rushing by and right the wrong. >.>
Speculating for the sake of fanfics can be fun, but no trying to prove that it's canon, hear? ^^
I. Vocabulary and generalities
Vocabulary:
The human genome (genetic make-up) is made up of 22 pairs of chromosomes and 1 pair of sexual chromosomes.
The sexual chromosomes are XX for women and XY for men.
A chromosome is a strand of DNA.
A gene is basically a portion of DNA (thus located on a chromosome) that codes for a specific trait (eye colour, but also various molecules needed by the body).
Genome inheritance scenario, as illustrated with one pair of chromosome (just repeat 22 more times to get the full genome):
Simple? ^^ A kid thus inherits half the genetic make-up of each parent.
From now on, for the specific case of the Byakugan and the Sharingan, I'll make the following assumptions, which are best-case scenarios for having the trait passed on:
- the Byakugan or the Sharingan is coded by just one gene located on one chromosome (the more genes on seperate chromosomes are needed, the least likely a kid would inherit all the necessary ones).
- it is not carried by the Y chromosome. This is a certainty in the case of the Byakugan. Since girls don't have Y chromosomes, Hinata and Hanabi would not have the Byakugan if it were carried by the Y chromosome.
- it is not carried by the X chromosome. If this were the case, men Sharingan or Byakugan wielders would not be able to pass on their bloodline to their sons (unless the mother does instead), only to daughters...
I'll thus use the following representations:
- given the first assumption, I'll only be representing the chromosome that supposedly carries the gene coding for the bloodline.
- I'll portray the chromosomes that have that gene in red, while I'll portray the "normal" ones in white. Normally, I should have just coloured a piece of the chromosome in red to symbolize the gene (that is unlikely to take up a whole chromosome), but whatever.
- if a combination basically gives the same results, I'll only draw it once and list the probability of it occuring on the side (so I don't have to draw 4 scenarios each time)
- in some scenarios I'll start with the "best case" ancestry (ie: the ancestor has the gene on both chromosome): with constant outbreeding, it won't make a big difference.
- the cases where the bloodline manifests will be framed in red
I'll thus study two scenarios:
- assuming that the gene is recessive, meaning that in order for the bloodline to manifest, the kid needs the gene on both chromosomes.
- assuming that the gene is dominant, meaning that in order for the bloodline to manifest, just having the gene on one chromosome is enough.
I'll note at this point that it's possible for chromosomes to swap a piece of themselves with another chromosome. But I won't be taking this into account because it works both ways, so doesn't change the odds.
II. First scenario: the gene is recessive
5 possibilities:
=> The only guarantee for the gene to manifest all the time if if both parents are "full" carriers so to say. Outbreeding will necessarily result in a child that won't manifest the bloodline, even if he has the gene on one of the chromosomes. The gene might not manifest for several generations unless the descendant meets both following conditions:
1. does have the recessive bloodline gene on one of his chromosomes (the odds decrease by half after each generation)
2. either has a child with someone who has the bloodline gene on both chromosomes (scenario 2 - 50% of the child showing the bloodline), or someone who has the bloodline on just on of the chromosomes (scenario 3 - 25% of the gene showing the bloodline).
A descendant who doesn't have the bloodline gene at all will obviously be unable to pass it on.
In the majority of cases, the descendants would thus not have the bloodline.
If the outbreeding is constant, then in this scenario, the gene would Never manifest. The better-case scenario is if the gene is Dominant.
III. Second scenario: the gene is dominant
Again, constant in-breeding is the only scenario that guarantees 100% success of passing on the trait.
Constant outbreeding means that with each generation, the chances of the gene being passed on is reduced by half. All children of an ancestor who has the gene on both chromosomes will manifest the bloodline, but after that, the probability of the gene passing on is reduced by half. So by the second generation, only half of the children would have the gene. By the third, only a quarter would have it. By the say... 10th generation, only one in 512 children would still have the bloodline.
For those who think this is sort of unfair, think of it this way: imagine this time that one of your ancestors has a dominant genetic disease, but that person and all of the descendants married healthy people. Wouldn't it be kind of unfair for the whole lineage to be doomed because of that one ancestor? =\ Crude example, but hey.
Finally, a majority of in-breeding with only very occasional outbreeding keeps the odds of not having kids without the bloodline relatively low (though it still isn't a 100% guarantee, children without the bloodline would show up eventually). It'd still have to be a vast majority of inbreeding though.
IV. Other ways to "increase" the odds :P
So by now, it's apparent that if All the Hyuugas for example truly do have the Byakugan (as said in one of the databooks), it'd truly imply a Massive amount of inbreeding. Not all Uchihas have the Sharingan so at least for Them it's not a problem, but as for the Hyuugas... But wait! Maybe there are other explanations! Well yes there are! =D
Alternate biological mechanisms that'd increase the odds!
- "magical genes that automatically pass on!" Note: this is stupid. There's no such thing as a magical gene that automatically passes on. =\ A piece of DNA is just another piece of DNA.
- the bloodline is not coded by DNA, but by RNA or something else. Or it's like... a virus! So it gets transmitted to the foetus no matter what. Note: this is also stupid. =\
- the mother's immune system automatically kills the foetus if it doesn't possess the Byakugan gene! This one is not only stupid, it works only with a Hyuuga female. Unless there's also a male equivalent that goes...
- the Hyuuga male sperm sprouts a substance that kills off feotuses without the Byakugan gene. Trust me, this isn't happening.
- ALL the other chromosomes of the Hyuuga genome have a "killer gene" that kills off the foetus unless it has the Byakugan gene. Since it's highly unlikely for the foetus to not inherit any other "Hyuuga chromosome" at all, it's significantly increase the odds.
Note: all of the above are completely stupid. Really. So don't go about as though they're possible explanations, because they're not.
Alternate social mechanisms that'd increase the odds! (much more likely than the above. Really.)
- genetic engineering! As in, selective in-vitro fertilization! Near guarantee of the gene passing on! Tedious though. This lack of good old-fashioned sex might explain why the Hyuugas are so uptight though. >.>
- selective abortion! Especially for those darn Hyuugas. Use the Byakugan to spot a "non-Byakugan" foetus before it's born, and abort it!
- selective infanticide! It'd be easy for the Hyuugas to spot a non-Byakugan child at birth, so there we go. It'd be harder for Uchihas though, since the trait doesn't manifest at birth, which might be why they're unable to go this route (lol).
- just go the "survival of the fittest" road! Have the non-Byakugan wielders go into dangerous enough scenarios and just wait for them to die off. How to convince them of this? Simple! Just implant some bullshit in their heads about having to prove that Hyuugas born without the Byakugan can be just as good and do everything those With the Byakugan can do. They'll die off in no time! =D As for the survivors, feh, they're easy to dispose of afterwards.
- preferential marriage and birth policies! If all marriages are arranged marriages, just prevent the non-Byakugan folks from ever marrying. Or have them marry sterile partners. In the meantime, encourage those With the Byakugan to reproduce more.
- or they can just use the non-Byakugan wielders as political tools and just marry them out. Bye!
- or they can simply kick them out when they're old enough and pretend they're not Hyuuga. Hey, better than selective infanticide. *shrugs*
V. Reviving the clan! Possible scenarios.
Well, so we have Sasuke here, and he kind of wanted to revive his clan. We'll be optimistic here and assume the best-case scenario of the Sharingan being a single dominant gene that's neither on the X nor the Y chromosome.
So how should he proceed?
1. The quantity road! Just have lots of children and there are bound to be some with the Sharingan. Polygamy or concubinage helps. Concubinage was used in some old Asian families such as in China, where concubinage was seen as nearly necessary to ensure that there's a male descendant (no, it no longer happens today, sorry). There'll be an overwhelming majority of non-Sharingan wielders after a few generations though.
2. The quality road! Either genetic engineering to ensure that the gene passes on, or selective abortion, or the likes. His wife (or wives) would kill him though.
3. The quantity then quality road! Start off by having lots of children. Have those with the Sharingan in-breed (after several more generations, if he can wait)! From then on it's smooth sailing! =D
Of course, we might end up with some other explanation such as the Sharingan actually being the product of Bijuu influence or whatnot (how is that possible? Maybe the bijuu chakra acts like a virus?), thus conventional genetics would not apply. Whatever. >.>
Another question is how any of the clans managed to start, assuming they only had one ancestor. Well, the following is possible (no more funny explanations, sorry): just one person with the bloodline wouldn't necessarily have started a whole clan. It is possible for several generations (maybe even with the help of polygamy and concubinage to help diversify) to have past since the first to manifest Byakugan or Sharingan. Thus, after several generations, there'd be a good number of bloodline wielders in that family as well as non-bloodline wielders. Eventually, after there are enough of them, those who do have the bloodline might have decided to group up and progressively move from out-breeding to in-breeding (after several generations it would have been possible for them to not always marry very close cousins and marry cousins several times removed instead, for example).
VI. Naruto genetics according to the anime! \.^_^.\ Or why you shouldn't take this too seriously?
Let's examine the anime!
Exhibit A: Uchiha Mikoto, ie Sasuke and Itachi's mother. Oy, she looks Surprisingly like a typical Uchiha. So is she an Uchiha by birth? I admit, I was quite surprised to see the resemblance to a typical Uchiha in the anime: since not all Uchihas have the Sharingan, they didn't necessarily have to constantly inbreed. Ah well, we'll never get confirmation.
Exhibit B: Chouji's mom. In the anime, there's apparently a screenshot of the parents coming to the academy to take home the kids, and we get a glimpse of the back of Chouji's mom. She is: fat and with pink hair. In short, she looked mighty like an Akimichi. Inbreeding?
Exhibit C: The Kaguya clan. My, they nearly all look exactly alike! And they all have the bloodline! As said, this is near impossible without near-constant inbreeding. Then again, this clan was violent, so was probably not above selective infanticide or the likes. Or the non-bloodliners were simply not shown. *shrugs*
Exhibit D: The Aburame clan (bikouchu filler arc). Again, they all look EXACTLY Alike. Bloodline or not, such a high degree of resemblance is only possible with near-constant inbreeding!
As for the Hyuugas, the databooks stated somewhere that "all Hyuugas have the Byakugan." And well, I've already explained That bit. Now they also state that the Uchiha, Hyuuga, Akimichi (yes) and Aburame are Konoha's four noble clans. Hmm...
So how do we interpret these troubling facts? =O
1. Indeed, all the major bloodline (or non-bloodline, but still noble) clans practice constant in-breeding to keep their line pure! The anime crew felt the need to make this obvious! \.o_o.\ |.o_o.| /.o_o./
2. ... or the anime crew simply don't do genetics either, and got lazy so just drew all of them alike.
Which one can it be? \.o_o.\ |.o_o.| /.o_o./
Incidentally, Kishimoto probably didn't think this through either. So really, don't take this Too seriously. =P
Hope this was informative.
I. Vocabulary and generalities
II. First scenario: the gene is recessive
III. Second scenario: the gene is dominant.
IV. Other ways to "increase" the odds
V. Reviving the clan! Possible scenarios.
VI. Naruto genetics according to the anime! \.^_^.\ Or why you shouldn't all take this too seriously.
I still say that Kishimoto probably didn't bother with genetics. ;)
I'll kill anyone by the way who decides to use this to argue that Neji and Hinata for example will be forced into an arranged marriage in CANON as a result. ^^ Before you die though, I'll be sure to drill into your head that "This is a shounen manga so there will be no forced relationships," hear? Anything that happens will be on a strictly voluntary basis. Besides, if Hinata or Neji are forced into Anything, you can expect the Main Character (tm) to come rushing by and right the wrong. >.>
Speculating for the sake of fanfics can be fun, but no trying to prove that it's canon, hear? ^^
I. Vocabulary and generalities
Vocabulary:
The human genome (genetic make-up) is made up of 22 pairs of chromosomes and 1 pair of sexual chromosomes.
The sexual chromosomes are XX for women and XY for men.
A chromosome is a strand of DNA.
A gene is basically a portion of DNA (thus located on a chromosome) that codes for a specific trait (eye colour, but also various molecules needed by the body).
Genome inheritance scenario, as illustrated with one pair of chromosome (just repeat 22 more times to get the full genome):
Simple? ^^ A kid thus inherits half the genetic make-up of each parent.
From now on, for the specific case of the Byakugan and the Sharingan, I'll make the following assumptions, which are best-case scenarios for having the trait passed on:
- the Byakugan or the Sharingan is coded by just one gene located on one chromosome (the more genes on seperate chromosomes are needed, the least likely a kid would inherit all the necessary ones).
- it is not carried by the Y chromosome. This is a certainty in the case of the Byakugan. Since girls don't have Y chromosomes, Hinata and Hanabi would not have the Byakugan if it were carried by the Y chromosome.
- it is not carried by the X chromosome. If this were the case, men Sharingan or Byakugan wielders would not be able to pass on their bloodline to their sons (unless the mother does instead), only to daughters...
I'll thus use the following representations:
- given the first assumption, I'll only be representing the chromosome that supposedly carries the gene coding for the bloodline.
- I'll portray the chromosomes that have that gene in red, while I'll portray the "normal" ones in white. Normally, I should have just coloured a piece of the chromosome in red to symbolize the gene (that is unlikely to take up a whole chromosome), but whatever.
- if a combination basically gives the same results, I'll only draw it once and list the probability of it occuring on the side (so I don't have to draw 4 scenarios each time)
- in some scenarios I'll start with the "best case" ancestry (ie: the ancestor has the gene on both chromosome): with constant outbreeding, it won't make a big difference.
- the cases where the bloodline manifests will be framed in red
I'll thus study two scenarios:
- assuming that the gene is recessive, meaning that in order for the bloodline to manifest, the kid needs the gene on both chromosomes.
- assuming that the gene is dominant, meaning that in order for the bloodline to manifest, just having the gene on one chromosome is enough.
I'll note at this point that it's possible for chromosomes to swap a piece of themselves with another chromosome. But I won't be taking this into account because it works both ways, so doesn't change the odds.
II. First scenario: the gene is recessive
5 possibilities:
=> The only guarantee for the gene to manifest all the time if if both parents are "full" carriers so to say. Outbreeding will necessarily result in a child that won't manifest the bloodline, even if he has the gene on one of the chromosomes. The gene might not manifest for several generations unless the descendant meets both following conditions:
1. does have the recessive bloodline gene on one of his chromosomes (the odds decrease by half after each generation)
2. either has a child with someone who has the bloodline gene on both chromosomes (scenario 2 - 50% of the child showing the bloodline), or someone who has the bloodline on just on of the chromosomes (scenario 3 - 25% of the gene showing the bloodline).
A descendant who doesn't have the bloodline gene at all will obviously be unable to pass it on.
In the majority of cases, the descendants would thus not have the bloodline.
If the outbreeding is constant, then in this scenario, the gene would Never manifest. The better-case scenario is if the gene is Dominant.
III. Second scenario: the gene is dominant
Again, constant in-breeding is the only scenario that guarantees 100% success of passing on the trait.
Constant outbreeding means that with each generation, the chances of the gene being passed on is reduced by half. All children of an ancestor who has the gene on both chromosomes will manifest the bloodline, but after that, the probability of the gene passing on is reduced by half. So by the second generation, only half of the children would have the gene. By the third, only a quarter would have it. By the say... 10th generation, only one in 512 children would still have the bloodline.
For those who think this is sort of unfair, think of it this way: imagine this time that one of your ancestors has a dominant genetic disease, but that person and all of the descendants married healthy people. Wouldn't it be kind of unfair for the whole lineage to be doomed because of that one ancestor? =\ Crude example, but hey.
Finally, a majority of in-breeding with only very occasional outbreeding keeps the odds of not having kids without the bloodline relatively low (though it still isn't a 100% guarantee, children without the bloodline would show up eventually). It'd still have to be a vast majority of inbreeding though.
IV. Other ways to "increase" the odds :P
So by now, it's apparent that if All the Hyuugas for example truly do have the Byakugan (as said in one of the databooks), it'd truly imply a Massive amount of inbreeding. Not all Uchihas have the Sharingan so at least for Them it's not a problem, but as for the Hyuugas... But wait! Maybe there are other explanations! Well yes there are! =D
Alternate biological mechanisms that'd increase the odds!
- "magical genes that automatically pass on!" Note: this is stupid. There's no such thing as a magical gene that automatically passes on. =\ A piece of DNA is just another piece of DNA.
- the bloodline is not coded by DNA, but by RNA or something else. Or it's like... a virus! So it gets transmitted to the foetus no matter what. Note: this is also stupid. =\
- the mother's immune system automatically kills the foetus if it doesn't possess the Byakugan gene! This one is not only stupid, it works only with a Hyuuga female. Unless there's also a male equivalent that goes...
- the Hyuuga male sperm sprouts a substance that kills off feotuses without the Byakugan gene. Trust me, this isn't happening.
- ALL the other chromosomes of the Hyuuga genome have a "killer gene" that kills off the foetus unless it has the Byakugan gene. Since it's highly unlikely for the foetus to not inherit any other "Hyuuga chromosome" at all, it's significantly increase the odds.
Note: all of the above are completely stupid. Really. So don't go about as though they're possible explanations, because they're not.
Alternate social mechanisms that'd increase the odds! (much more likely than the above. Really.)
- genetic engineering! As in, selective in-vitro fertilization! Near guarantee of the gene passing on! Tedious though. This lack of good old-fashioned sex might explain why the Hyuugas are so uptight though. >.>
- selective abortion! Especially for those darn Hyuugas. Use the Byakugan to spot a "non-Byakugan" foetus before it's born, and abort it!
- selective infanticide! It'd be easy for the Hyuugas to spot a non-Byakugan child at birth, so there we go. It'd be harder for Uchihas though, since the trait doesn't manifest at birth, which might be why they're unable to go this route (lol).
- just go the "survival of the fittest" road! Have the non-Byakugan wielders go into dangerous enough scenarios and just wait for them to die off. How to convince them of this? Simple! Just implant some bullshit in their heads about having to prove that Hyuugas born without the Byakugan can be just as good and do everything those With the Byakugan can do. They'll die off in no time! =D As for the survivors, feh, they're easy to dispose of afterwards.
- preferential marriage and birth policies! If all marriages are arranged marriages, just prevent the non-Byakugan folks from ever marrying. Or have them marry sterile partners. In the meantime, encourage those With the Byakugan to reproduce more.
- or they can just use the non-Byakugan wielders as political tools and just marry them out. Bye!
- or they can simply kick them out when they're old enough and pretend they're not Hyuuga. Hey, better than selective infanticide. *shrugs*
V. Reviving the clan! Possible scenarios.
Well, so we have Sasuke here, and he kind of wanted to revive his clan. We'll be optimistic here and assume the best-case scenario of the Sharingan being a single dominant gene that's neither on the X nor the Y chromosome.
So how should he proceed?
1. The quantity road! Just have lots of children and there are bound to be some with the Sharingan. Polygamy or concubinage helps. Concubinage was used in some old Asian families such as in China, where concubinage was seen as nearly necessary to ensure that there's a male descendant (no, it no longer happens today, sorry). There'll be an overwhelming majority of non-Sharingan wielders after a few generations though.
2. The quality road! Either genetic engineering to ensure that the gene passes on, or selective abortion, or the likes. His wife (or wives) would kill him though.
3. The quantity then quality road! Start off by having lots of children. Have those with the Sharingan in-breed (after several more generations, if he can wait)! From then on it's smooth sailing! =D
Of course, we might end up with some other explanation such as the Sharingan actually being the product of Bijuu influence or whatnot (how is that possible? Maybe the bijuu chakra acts like a virus?), thus conventional genetics would not apply. Whatever. >.>
Another question is how any of the clans managed to start, assuming they only had one ancestor. Well, the following is possible (no more funny explanations, sorry): just one person with the bloodline wouldn't necessarily have started a whole clan. It is possible for several generations (maybe even with the help of polygamy and concubinage to help diversify) to have past since the first to manifest Byakugan or Sharingan. Thus, after several generations, there'd be a good number of bloodline wielders in that family as well as non-bloodline wielders. Eventually, after there are enough of them, those who do have the bloodline might have decided to group up and progressively move from out-breeding to in-breeding (after several generations it would have been possible for them to not always marry very close cousins and marry cousins several times removed instead, for example).
VI. Naruto genetics according to the anime! \.^_^.\ Or why you shouldn't take this too seriously?
Let's examine the anime!
Exhibit A: Uchiha Mikoto, ie Sasuke and Itachi's mother. Oy, she looks Surprisingly like a typical Uchiha. So is she an Uchiha by birth? I admit, I was quite surprised to see the resemblance to a typical Uchiha in the anime: since not all Uchihas have the Sharingan, they didn't necessarily have to constantly inbreed. Ah well, we'll never get confirmation.
Exhibit B: Chouji's mom. In the anime, there's apparently a screenshot of the parents coming to the academy to take home the kids, and we get a glimpse of the back of Chouji's mom. She is: fat and with pink hair. In short, she looked mighty like an Akimichi. Inbreeding?
Exhibit C: The Kaguya clan. My, they nearly all look exactly alike! And they all have the bloodline! As said, this is near impossible without near-constant inbreeding. Then again, this clan was violent, so was probably not above selective infanticide or the likes. Or the non-bloodliners were simply not shown. *shrugs*
Exhibit D: The Aburame clan (bikouchu filler arc). Again, they all look EXACTLY Alike. Bloodline or not, such a high degree of resemblance is only possible with near-constant inbreeding!
As for the Hyuugas, the databooks stated somewhere that "all Hyuugas have the Byakugan." And well, I've already explained That bit. Now they also state that the Uchiha, Hyuuga, Akimichi (yes) and Aburame are Konoha's four noble clans. Hmm...
So how do we interpret these troubling facts? =O
1. Indeed, all the major bloodline (or non-bloodline, but still noble) clans practice constant in-breeding to keep their line pure! The anime crew felt the need to make this obvious! \.o_o.\ |.o_o.| /.o_o./
2. ... or the anime crew simply don't do genetics either, and got lazy so just drew all of them alike.
Which one can it be? \.o_o.\ |.o_o.| /.o_o./
Incidentally, Kishimoto probably didn't think this through either. So really, don't take this Too seriously. =P
Hope this was informative.