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A crazy theory on Tyrion


Ygrain

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I think the answer is, "Genetics matter when Martin wants them to, and behave how Martin wants them to."

I have no idea why Tyrion has only eye that's a different color from the other one. I don't know what it means, if it means anything. I do know that Shiera Seastar had a blue eye and a green eye, not a black one, if you want to get into the nitty gritty of it. ;)

Meh, I don't even really buy the theory, but there is evidence for it. And people focus on genetics because GRRM made it a plot-point. That was all I was tryin to say. ;)

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Not under the basic Mendelian genetics: aa + aa = aa, there's nowhere to obtain the dominant variant of the gene from. It works the other way round: blackhaired parents can easily have blond children, once the recessive gene was introduced into both lineages: Aa + Aa = AA(pure black, children always blackhaired, no matter what variant they inherit from the other parent), Aa (blackhaired but passing on the blonde gene), or aa (lo! a blondie!). The Aa = blackhaired is what brings Jon Arryn and Ned to the conclusion that Robert can't have fathered Cersei's children.

- I just hope the pattern applies fully to hair colour as well, since the book example is for brown and blue eyes, and here I've almost exhausted my knowledge of genetics :-) However, I'll venture a little guess: as I looked up Shiera, she had eyes of blue and green. The green colour genes do not manifest in such a simple way (observation from my family, where grandfather had brown eyes, grandmother green, and my mother ended up with eyes which looked light brown but were, in fact, green at the rim and brown around the pupil) but I think I can safely bet that both the green and blue colour already had to be there in order to manifest, and that the disorder only caused the genes to be paired differently in various parts of the body.

In this example you are assuming that because both parents have the recessive phenotype (blonde), they are both homozygous, but either one or both can be heterozygous.

(using ‘H’ and ‘h’ for hair colour)

For instance, a ‘blonde’ homozygous with be hh whereas a blonde heterozygous will be Hh.

A blonde homozygous with a blonde heterozygous can produce dark-haired children; if both blonde parents are heterozygous, the chances of getting a dark-haired kid are even more likely.

:-)

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Meh, I don't even really buy the theory, but there is evidence for it. And people focus on genetics because GRRM made it a plot-point. That was all I was tryin to say. ;)

Heh, I'm not even sure I'm buying it myself ;-)

If Tywin had any idea that Tyrion really wasn't his, he would never have put on for so long that he was. He would've used any excuse he had to disown the Imp.

I believe he would have gladly done that even if he was 100% sure the Imp was his. The question is, what excuse could he use except denying fathering Tyrion? What a blow to his pride: Lord Tywin Lannister has a cuckoo! Were I him, I'd rather swallow my pride and claim the misfit for my own than become an even worse laughing stock.

I think the answer is, "Genetics matter when Martin wants them to, and behave how Martin wants them to."

I have no idea why Tyrion has only eye that's a different color from the other one. I don't know what it means, if it means anything. I do know that Shiera Seastar had a blue eye and a green eye, not a black one, if you want to get into the nitty gritty of it. ;)

I don't think we will be able to establish how much GRRM is really into genetics until the end of the series but so far, he has been very thorough and consistent in details of culture and history. I'd be very surprised if he never bothered to study something about genetics. Mind you, he uses it not just in the Jeoffrey plot but also with the Starks (the heritage from the First people) and Targaryens (remember how the dragons likes Ben Plumm because of that drop of Targ blood?)

As for Shiera's different eye colours, I don't think the disorder establishes the colour as such but rather mismatches the already present genes. - Which brings me back to the original question: where the heck did the black colour in the lineage of blondes come from? - Were it at a later time, I'd say that Robert must have been the culprit, but with things as they are, he would have had to use a time machine :D

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In this example you are assuming that because both parents have the recessive phenotype (blonde), they are both homozygous, but either one or both can be heterozygous.

(using ‘H’ and ‘h’ for hair colour)

For instance, a ‘blonde’ homozygous with be hh whereas a blonde heterozygous will be Hh.

A blonde homozygous with a blonde heterozygous can produce dark-haired children; if both blonde parents are heterozygous, the chances of getting a dark-haired kid are even more likely.

:-)

But if this is the plain and simple case of full dominance, then Hh combination always displays the features of the dominant gene. If a heterozygous blonde was possible, Jon Arryn and Ned wouldn't have been able to draw the conclusion. - But again, I'm no expert and I only presume that the light hair colour gene behaves the same as the light eye colour one.

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But if this is the plain and simple case of full dominance, then Hh combination always displays the features of the dominant gene. If a heterozygous blonde was possible, Jon Arryn and Ned wouldn't have been able to draw the conclusion. - But again, I'm no expert and I only presume that the light hair colour gene behaves the same as the light eye colour one.

The light eye colour is even more complicated...

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But if this is the plain and simple case of full dominance, then Hh combination always displays the features of the dominant gene. If a heterozygous blonde was possible, Jon Arryn and Ned wouldn't have been able to draw the conclusion. - But again, I'm no expert and I only presume that the light hair colour gene behaves the same as the light eye colour one.

Well, we haven't even brought incomplete dominance into the discussion yet.... :-)

Just for fun:

Eye color is a polygenic phenotypic character and is determined by two distinct factors: the pigmentation of the eye's iris[1][2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.[3]

http://en.wikipedia.org/wiki/Eye_color

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Oww, school rules don't apply! My worldview is in ruins? :-) - Yeah, I know about incomplete dominance and co-dominance... vaguely. However: say that we have the book example of brown (A, dominant) and blue (a, recessive), represented by AA and aa parents and not complicated by any other genes; does the rule of Aa = always brown hold? And, does the rule apply analogically to black and blonde hair colour, i.e., is blonde caused by an equally recessive gene and requiring a homozygous individual to manifest?

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Oww, school rules don't apply! My worldview is in ruins? :-) - Yeah, I know about incomplete dominance and co-dominance... vaguely. However: say that we have the book example of brown (A, dominant) and blue (a, recessive), represented by AA and aa parents and not complicated by any other genes; does the rule of Aa = always brown hold? And, does the rule apply analogically to black and blonde hair colour, i.e., is blonde caused by an equally recessive gene and requiring a homozygous individual to manifest?

Brown is, I believe, the dominant genotype/phenotype. So Aa would always be brown, yes.

Hair is trickier because you're dealing with several alleles, not just two. Typically though, the more dominant alleles, the darker the hair, and the more recessive alleles, the lighter the hair. This is where Martin's genetics kind of deviate from reality: Even with the Baratheon mega-black-hair genes, reproducing with a blonde (i.e. someone with several recessive alleles) would probably produce a child with dark-but-not-black hair. So while, in reality, Cersei's children were all too light-haired to be fathered by Robert, nor would Robert and Cersei (or Robert and any of his fair-haired ladyfriends) have produced perfectly raven-haired children, as I understand it.

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Oww, school rules don't apply! My worldview is in ruins? :-) - Yeah, I know about incomplete dominance and co-dominance... vaguely. However: say that we have the book example of brown (A, dominant) and blue (a, recessive), represented by AA and aa parents and not complicated by any other genes; does the rule of Aa = always brown hold? And, does the rule apply analogically to black and blonde hair colour, i.e., is blonde caused by an equally recessive gene and requiring a homozygous individual to manifest?

What about those Ghicari, with their mixture of red and black hair (red hair genes act way differently than just brown/blond)? Or was that dye?

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Brown is, I believe, the dominant genotype/phenotype. So Aa would always be brown, yes.

That depends. Are we talking both parents? And even with both parents having brown eyes, they can have a blue-eye child if they are heterozygous.

Hair is trickier because you're dealing with several alleles, not just two. Typically though, the more dominant alleles, the darker the hair, and the more recessive alleles, the lighter the hair. This is where Martin's genetics kind of deviate from reality: Even with the Baratheon mega-black-hair genes, reproducing with a blonde (i.e. someone with several recessive alleles) would probably produce a child with dark-but-not-black hair. So while, in reality, Cersei's children were all too light-haired to be fathered by Robert, nor would Robert and Cersei (or Robert and any of his fair-haired ladyfriends) have produced perfectly raven-haired children, as I understand it.

It wouldn't be the most likely outcome, but it is possible. There's no way of determining, for instance, all the Baratheon possibilities in terms of phenotype without knowing their ancestry and doing a genetic mapping of all those who came before them. I mean, even knowing the colour of Robert's parents and grandparents eye colour wouldn't be enough because we'd need to know whether they are heterozygous or homozygous...

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That depends. Are we talking both parents? And even with both parents having brown eyes, they can have a blue-eye child if they are heterozygous.

It wouldn't be the most likely outcome, but it is possible. There's no way of determining, for instance, all the Baratheon possibilities in terms of phenotype without knowing their ancestry and doing a genetic mapping of all those who came before them. I mean, even knowing the colour of Robert's parents and grandparents eye colour wouldn't be enough because we'd need to know whether they are heterozygous or homozygous...

What do you mean by heterozygous or homozygous? Aa being hetero and AA/aa being homozygous?

ETA: I think it's fairly clear that the books implied that Robert was BB (black hair) and bb (blue eyes). It doesn't really explain why all but one of Ned's trueborn children (with Cat) have red hair, since it's a recessive (in his case). Possible, but the odds are very low.

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Just done my research: http://en.wikipedia....y_of_hair_color "A person with a brown allele will have brown hair; a person with no brown alleles will be blond"

Not exactly. Somene who inherits the dominant allele from both parents will have brown eyes. That does not mean that if both parents have brown eyes, their children will have brown eyes as well; the parents can both be heterozygous with dominant phenotype (brown eyes).

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That depends. Are we talking both parents? And even with both parents having brown eyes, they can have a blue-eye child if they are heterozygous.

If we have one AA parent (brown) and one aa parent (blue), they would not produce a blue-eyed child. All four possible outcomes would be Aa, which would produce a brown-eyed kid. The question posed was one of, "What about Aa?" so that's what I answered. And yes, obviously I know that a brown-eyed Aa parent and a blue-eyed aa parent could produce a blue-eyed child (25% chance, I believe). But that wasn't the question — it was about Aa specifically. If you yourself are Aa, then you'd have, barring some kind of other issue, brown eyes.

It wouldn't be the most likely outcome, but it is possible. There's no way of determining, for instance, all the Baratheon possibilities in terms of phenotype without knowing their ancestry and doing a genetic mapping of all those who came before them. I mean, even knowing the colour of Robert's parents and grandparents eye colour wouldn't be enough because we'd need to know whether they are heterozygous or homozygous...

If the Baratheons are all blue-eyed (and they must be, it keeps getting passed down), they'd have to be homozygous recessive, or, at the very least, heterozygous dominant (the overwhelming frequency of blue eyes points to a large number of homozygous recessive Baratheons, though). I don't think you can have a heterozygous recessive allele pair for eyes. You're heterozygous dominant, homozygous dominant, or homozygous recessive. Other variations, like green eyes, would be caused by some other kind of pigment.

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What do you mean by heterozygous or homozygous? Aa being hetero and AA/aa being homozygous?

Heterozygous have two different alleles for a single trait; homozygous have identical alleles for a single trait.

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Heterozygous have two different alleles for a single trait; homozygous have identical alleles for a single trait.

Okay, so AA/aa=homozygous. Aa=heterozygous. Gotcha. Thanks. It's been a decade since I've done any kind of genetics in school!

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I'm still to sleepy to go into a full genetics essay, and it would be beside the point as I don't think it will matter in the books.

My apologies if I've replied to the wrong question, as I said, still very sleepy.

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Kissdbyfire:

Heterozygous parents can produce children of either colour, but a blonde person must be homozygous recessive, and there is no way blonde Lord Tywin and blonde lady Joanna could produce a child with black hair. - Unless Joanna was not blonde; don't remember if her hair colour was ever mentioned but since it has been frequently pointed out that all Lannisters display various shades of blonde, I assume that she was in this a typical Lannister.

edit: -ah, I see we're at a misconception here. Good night :-)

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Kissdbyfire:

Heterozygous parents can produce children of either colour, but a blonde person must be homozygous recessive, and there is no way blonde Lord Tywin and blonde lady Joanna could produce a child with black hair. - Unless Joanna was not blonde; don't remember if her hair colour was ever mentioned but since it has been frequently pointed out that all Lannisters display various shades of blonde, I assume that she was in this a typical Lannister.

edit: -ah, I see we're at a misconception here. Good night :-)

I think this is a case of Martin playing fast and loose with the genetics a bit. It might actually be intentional, giving people the idea that maybe Tyrion isn't Tywin's. But I'm about 99% sure that he is, for the reasons people have given.

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This thread seems to be going towards 'genetics could be a plot point in Tyrion's case because they were a plot point with Cersei's bastards'.

I think that wrong, as genetics were not important in the prior case - the seed is strong was the plot point, and that is fake genetics. The reasoning was that as whenever the Stag and Lion mated historically the stag won, in this case Robert and Cerseis kids should have been blond. In real world genetics that would mean that Lannister and Bareathons already have similar genes, diluted by all the other families they have bred into, and that there would not be a gurantee of Robert having dark haired kids.

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