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House and Mendelian genetics - The Phantom Librarian
Spewing out too many words since November 2003
House and Mendelian genetics
So I watched the House rerun on USA network, and the B-plot involved a patient who wouldn't get surgery on a tumor, and House gets a brainwave when he sees a picture of her kids and realizes that her husband isn't their father (at least for some of them). Because both of them have brown eyes, but a couple of the kids have blue and green eyes.

Now, am I misremembering high school genetics, or are brown eyes a dominant trait? In other words, two brown-eyed people could be carrying recessive genes for other eye colors (as opposed to recessive blue eyes, where if a brown-eyed child appeared, you'd have to have a look at the mailman). So if the wife was, say, Brown-Blue, and the husband was Brown-Green, then the kids could get green or blue eyes (I think, though the green might be dominant over the blue, thus making blue unlikely, but I don't think eye color is quite as simple as that--I'm just pretty sure that the darker eye colors, being dominant, don't preclude lighter ones).
29 comments or Leave a comment
gehayi From: gehayi Date: December 24th, 2006 05:18 am (UTC) (Link)
You're absolutely right, and House messed up the Mendelian laws of genetics.
lilacsigil From: lilacsigil Date: December 24th, 2006 05:21 am (UTC) (Link)
You're correct. Both my parents have brown eyes - I have green, and both my brothers have blue, so I caught this one immediately!

Polite Dissent has good medicine-based episode guides.
lilacsigil From: lilacsigil Date: December 24th, 2006 05:22 am (UTC) (Link)
Correct link is here, sorry.
fernwithy From: fernwithy Date: December 24th, 2006 05:35 am (UTC) (Link)
Oo, neat link! :D
hermia7 From: hermia7 Date: December 24th, 2006 05:25 am (UTC) (Link)
Yes, you're right, and I think green and brown actually combine to make hazel--at least, that is the case for my husband's half brother, who has hazel eyes, a brown-eyed mother and a green-eyed (truly, it was crazy) father.

BTW, it was nice to meet you a couple weeks ago!
fernwithy From: fernwithy Date: December 24th, 2006 05:36 am (UTC) (Link)
You, too!

I'm the blue-eyed daughter of a brown-eyed woman, but my father was blue-eyed and my maternal grandmother is as well.
hermia7 From: hermia7 Date: December 24th, 2006 05:44 am (UTC) (Link)
For me: Blue eyes, mom = blue, dad = brown. Brother has brown.
jetamors From: jetamors Date: December 24th, 2006 05:26 am (UTC) (Link)
Yup. I'm another living counter-example: both parents with brown eyes, and I ended up with hazel.
purple_ladybug1 From: purple_ladybug1 Date: December 24th, 2006 05:28 am (UTC) (Link)
Hahaha, I haven't looked at genetics since the 8th grade. But it appears others have more knowledge, and answered your question, and quenched my curiousity.
redlily From: redlily Date: December 24th, 2006 05:30 am (UTC) (Link)
Hey, I just watched that episode not an hour ago on DVD. I think the point here is that House combined his genetic knowledge with his observations of the woman's behavior. Also, both of the "parents" in question seemed to be of Hispanic descent, which would substantially lessen the probability of both of them having a recessive blue- or green-eyed gene. Finally, we've seen House do this a couple times (draw people out through faulty medical assumptions, c.f. the time he told the married couple you can get syphilis via toilet seats), and if he'd been wrong, he would've segued into another explanation for her unwillingness to be operated on.

I mean, you could say that I'm giving House too much credit, but unless we're talking about Vicodin, it seems you really can't give House enough credit.
fernwithy From: fernwithy Date: December 24th, 2006 05:38 am (UTC) (Link)
I'd make the assumption that he's looking at lots of things, though House would usually make a snarky comment about the likelihood of possible recessive genes if he was taking that into account.
redlily From: redlily Date: December 24th, 2006 05:45 am (UTC) (Link)
*shrug* I guess I'd just attribute that to him not wanting to give her a possibility for evasion. She seemed pretty spunky and quick to me, and she would've seized on any chance to deny the affairs she apparently had.

Of course, then there's the fact that House thinks, like, 50% of kids are actually products of extramarital affairs. Obviously I'm exaggerating, but I just watched an early first-season one (maybe the second or third episode ever?) where he bets that the kid isn't the father's. (He turns out to be adopted.)
victorialupin From: victorialupin Date: December 24th, 2006 05:30 am (UTC) (Link)
Perhaps the writers meant to do it the other way around, but screwed-up. Blue-eyed parents with brown-eyed kids would have worked for the story.
fernwithy From: fernwithy Date: December 24th, 2006 05:37 am (UTC) (Link)
Or maybe it was originally written as blue-eyed, but they cast a brown-eyed actress and changed the line?
victorialupin From: victorialupin Date: December 24th, 2006 06:24 pm (UTC) (Link)
Probably. Somewhere along the line, somebody changed it and didn't realize the significance.
From: (Anonymous) Date: December 24th, 2006 05:57 am (UTC) (Link)
Someone also explained to me once how you could get a brown eyed child from blue eyed parents.

I may not be remembering that right but I did know a woman who, when I first met her, had hazel eyes like her mother's. Over a period of years, they became hazel with blue flecks, then blue with hazel flecks. Finally, they were blue eyes just like her father's.

I also knew a girl with one brown eye and one eye that was about a third or a quarter brown and then turned green. There was a straight line where the change occurred in the one eye.

I've only seen House a few times, and it just hasn't worked for me (apologies to all fans). On the one hand, I'm glad to see a show where the pain-in-the-neck doctor is the best one rather than the guy who only seems to be there to make you appreciate the saints in surgical garb who make up all the competent doctors on the show. Most medical people have to find some way to emotionally distance themselves from what they deal with every day. In that respect, House strikes me as realistic enough. He's a brilliant surgeon who does a really good job at seeing his patients as puzzles rather than people he feels emotionally connected to.

But I've seen enough on that show where I'm going, "They missed WHAT?"
Good grief, the episode where the couple didn't know they were half-brother and sister (and where nobody in the families had let either one of them know they might carry a potentially lethal gene that the dad was already taking medication for [and the son knew he was taking medication, he just thought it was drugs (did I misunderstand that part?)]).

The doctor who didn't want to tell them they might be brother and sister also tried to reassure them that children from that inbred a union wouldn't necessarily be at high risk of genetic problems.

Er, skipping debate on that as a general rule, can we cut to the chase? Each of them already carried a potentially lethal gene. Its lethal condition was recognized as a dominant, but did the doctors check what happened to people with TWO of it?

A rare condition, lethal when it manifests without modern medicine, doesn't really sound like one of the ones likely to have many people walking around with TWO of the genes instead of one. Think female hemophiliacs who used to be practically unknown before treatments allowed men carrying the gene to live long enough to have children. Even so, they remain very rare.

So, this couple has at least a 75% chance that every child they might have will have this condition. They have a 25% chance of finding out whether what they're experiencing is just a mixed dominant manifestation of the trait and that the double gene is much, much worse.

Sorry. It was just one of those things that drove me up the wall.

I just wouldn't be surprised if House saw a family who had only daughters and started talking about the genetic improbability of a guy with a YX configuration nevery handing on his Y and coming to the brilliant conclusion that the father must really be a woman.

fernwithy From: fernwithy Date: December 24th, 2006 06:08 am (UTC) (Link)
Yeah, my mom's a nurse, and it annoys her medically as well. Me, I just like snarko-doc, and it's usually well-written, and the soap opera aspects aren't generally too overwrought (I stopped watching E.R. somewhere around season six when it turned into just one big sudsfest).
tdu000 From: tdu000 Date: December 24th, 2006 07:54 am (UTC) (Link)
I've a friend who's a high school science teacher (ages 12 to 18) and she's been told not to use eye colour as an example in teaching genetics as children can suddenly work things out about their parentage that they previously didn't know. The school doesn't want to deal with the possible fall-out! It's a nuisance as it's an easy example to use in class.
fernwithy From: fernwithy Date: December 24th, 2006 02:39 pm (UTC) (Link)
Oh, that's kind of irritating. My 9th grade science teacher used eye color as a very quick example, with himself and his wife as the primary sample (as they both had little blue eyes, recessive, and pointed out that if a kid showed up with big brown ones, he'd get really suspicious... of course, the fact that it was a small town and well knew all of his blue-eyed kids helped).
tdu000 From: tdu000 Date: December 24th, 2006 10:21 pm (UTC) (Link)
I think one of the teachers had had the experience of a student working out that his father wasn't his biological father and the school decided they didn't want to get involved in family scandals. I can see their point, it isn't something a child needs to learn in the middle of a science lesson.
hymnia From: hymnia Date: December 24th, 2006 07:22 pm (UTC) (Link)
That actually happened in my mom's high school biology class. One of her classmates found out she was adopted because of the eye color thing.

In my college biology class, the teacher used the example of blood types instead, and one of the girls in the class got upset with him, because she said her two-year-old son's blood type would, according to the logic he was presenting, not be possible if her boyfriend was the father, but she knew her boyfriend was the father. My teacher finally relented and said there were rare cases where the phenotype (expressed trait) didn't match the genotype (genetic code). In other words, a person might have a genetic code for A blood, but for some reason--another gene interferring or something like that--they wouldn't actually have the A antibodies in their blood, so they would test as type O.

Personally, I think she must've just got mixed up about either her boyfriend's or her son's blood type.
divabat From: divabat Date: December 25th, 2006 09:13 am (UTC) (Link)
Interesting! Our school used eye colors as a generic genetics thing - brown/black eyes were dominant, blue eyes were recessive.

then again, this is Malaysia, where blue eyes are uncommon enough to make people wonder...
tdu000 From: tdu000 Date: December 25th, 2006 09:31 am (UTC) (Link)
I can see that where a country has a predominant eye colour that you don't need a biology lesson to point out the obvious. In Australia we have the whole spectrum so the inheritance issues are less obvious.
ratcreature From: ratcreature Date: December 24th, 2006 10:17 am (UTC) (Link)
I think I read somewhere that the eyecolor genetics actually are more complicated than being determined by just one gene pair like that with simple dominant/recessive Mendelian rules, and that there are more gene pairs involved which influence eye color, at least three, and that it is in fact possible for two blue eyed parents to have a brown eyed child genetically, even though that is very rare.

But the basic mechanism I remember learning in school was like you said. Sadly since everybody in my family has had some version of blue eyes for at least three generations (the only variations are that after all what's called "blue" can be anything from actual blue to a kind of muddy dishwater color with yellowish flecks like mine which only look truly "blue" in the right environmental light), I couldn't imagine any salacious family secrets even with that simplified explanation.
From: (Anonymous) Date: December 24th, 2006 09:12 pm (UTC) (Link)
This is true. Eye color is an example of a multiple allele which is the offical name for when a phenotype ( a trait that is observablable by looking at someone) requires a combination of several genes.

sreya From: sreya Date: December 24th, 2006 12:36 pm (UTC) (Link)
Yeah, I think they pretty much blew it on that one. But then, I tend to be a skeptic on how hard and fast Mendelian genetic rules actually are - I tend to think that one characteristic may be dominant for some families and recessive in others and you can't REALLY predict individual characteristics that way. Not that I'm a medical expert or anything, just observations from my own family lines.
From: lianna_blanca Date: December 24th, 2006 09:42 pm (UTC) (Link)
This is the reason why I always thought James Potter had blue eyes - until JKR told us they were brown. That still irks me, actually. A brown-eyed father is far more likely to pass on that colour than a green-eyed mother. Poor Harry.

(Though, going a bit off-track here, I still wonder if Merope's dying wish affected Tom's appearance, and if so, perhaps magical genetics have more complexities. I do NOT want to try and figure out the dominants and recessives for squibs and so on - though there are some facinating discussions around. Either way, this isn't the place.)
fernwithy From: fernwithy Date: December 24th, 2006 09:55 pm (UTC) (Link)
Actually, according to the scene, he has hazel eyes, which is a brown-green mix, so probably means he's got a green gene in there somewhere, and Harry is a straight green-green. But even if he had brown eyes, he could be heterozygotic brown and have passed on a blue or green gene to Harry. The point is that people whose eyes express the dominant color--brown--could be carrying just about anything in terms of non-expressed genes.

JKR claims magic is dominant, but if that were so, more or less everyone would have it by now!
divabat From: divabat Date: December 25th, 2006 09:15 am (UTC) (Link)
Isn't it just an issue of the magical world being largely inbred, though? (Which does bring up interesting questions about Hermione's parentage.)
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