An argument for more cats and fewer humans in genetics class

March 1, 2015 1:20 PM

Unfortunately, what textbooks, lab manuals and web pages say about these human traits is mostly wrong. Most of the common, visible human traits that are used in classrooms do NOT have a simple one-locus, two-allele, dominant vs. recessive method of inheritance. Rolling your tongue is not dominant to non-rolling, unattached earlobes are not dominant to attached, straight thumbs are not dominant to hitchhiker's thumb, etc.
posted by sciatrix (41 comments total)

"more cats and fewer humans in genetics class"

I keep trying to do this, because none of the humans in the biology program can keep up a soothing purr, and every time faculty try to pet them they file sexual harassment complaints, but the Supreme Court keeps striking down my catfirmative action plan on the grounds that the cats aren't "qualified" because instead of taking the SAT, they just sat down on the paper and groomed themselves for a while. I'D LIKE TO SEE YOU LICK YOUR OWN BUTT, SCALIA. Then we can talk about "qualifications."
posted by Eyebrows McGee at 1:34 PM on March 1, 2015 [49 favorites]

The white locus is useful because the dominant W allele, which produces all-white cats, is quite rare; this helps students understand that a "dominant" allele, in genetics, is one that determines the phenotype of the heterozygote, not the most common allele in the population

This is about teaching kids and I got to this part and I am clearly stupid because I was like "determines what's that of the who, now?" and now I need to lie down and pet me a kitty.
posted by billiebee at 1:55 PM on March 1, 2015 [3 favorites]

But the parts of your tongue where you taste sweet and sour, that's straightforward dominant/recessive, right?
posted by Segundus at 1:57 PM on March 1, 2015 [5 favorites]

I'D LIKE TO SEE YOU LICK YOUR OWN BUTT, SCALIA.

I would very much like to not see that.
posted by Ursula Hitler at 1:59 PM on March 1, 2015 [3 favorites]

But the parts of your tongue where you taste sweet and sour, that's straightforward dominant/recessive, right?

That is just a straight up misconception, sorry. D:
posted by sciatrix at 2:00 PM on March 1, 2015 [4 favorites]

This is incredibly frustrating when you're a student because what your teacher tells you simply doesn't fit with what you know about your family. If you continue studying genetics, it's also harmful because usually teachers who are comfortable with that kind of oversimplification are big on oversimplifying-to-the-point-of-misleading about other things.

It also leaves students who don't continue on with the very unfortunate idea that most traits are Mendelian, which helps keep the level of discourse around genetics research and ethics very low.

But cats are great. My high school genetics teacher was OBSESSED with cats. I was thoroughly sick of cat genetics by the end of the class, but very grateful after I'd been through my first college level genetics course (which focused on humans). The cat problems were harder and more realistic and had better pictures.
posted by congen at 2:03 PM on March 1, 2015 [8 favorites]

I use kitties in my class! The standard labs, alas, do use human traits but we start out with a giant disclaimer about how these are Mendellianish and more complicated, but generally mimic Mendellian inheritance...
posted by ChuraChura at 2:03 PM on March 1, 2015 [2 favorites]

This is about teaching kids and I got to this part and I am clearly stupid because I was like "determines what's that of the who, now?" and now I need to lie down and pet me a kitty.

Basically, they're saying that if a cat has one W (dominant) copy and one w (recessive) copy [i.e. is heterozygous], their appearance [phenotype] will be white. People find this counterintuitive because we feel like the thing we see most often "should" represent the dominant version of the trait, and there aren't that many all-white cats. But if lots and lots of cats are ww (not-all-white) or even Ww (all-white but could pass on the not-all-white copy), you get a lot of ww (not-all-white) kittens.
posted by dorque at 2:03 PM on March 1, 2015 [2 favorites]

Yeah, cats are a great example for reminding people that dominant =/= most common (which is a frequent misconception)!
posted by ChuraChura at 2:05 PM on March 1, 2015

Thanks. This led me to finding another article about eye colour. My siblings and I have brown eyes and my sister's husband has blue eyes. I always thought brown was the dominant gene so I never understood why her two kids have blue eyes. I *think* I understand it now. (Though I'm still raging because he wins all the decisions and I was not pleased that he even won the one that I thought was a biological given...)
posted by billiebee at 2:13 PM on March 1, 2015 [1 favorite]

Can this explain why there won't be any more blondes in a hundred years?
posted by Navelgazer at 2:15 PM on March 1, 2015 [2 favorites]

Well at least I have discovered the concept of "middle phalangeal hair," which explains the single hair on my middle fingers. Now I just need an explanation why it is only my middle fingers, left and right, and no other fingers. Now I am checking my toes.. no, I better stop here.
posted by charlie don't surf at 2:18 PM on March 1, 2015

Eyebrows McGee: "I'D LIKE TO SEE YOU LICK YOUR OWN BUTT, SCALIA."

Well, every opinion he writes is equivalent to fluffing his self-exalted intellect, so...
posted by notsnot at 2:33 PM on March 1, 2015

I'm teaching plant systematics this summer and now I am desperately trying to figure out how to work in more cats.
posted by pemberkins at 2:37 PM on March 1, 2015 [2 favorites]

And when one of your students asks about calico cats, you can tell them the fascinating story of X inactivation.
posted by clawsoon at 2:40 PM on March 1, 2015 [6 favorites]

This is where it would be apropos to recommend Laura Gould's excellent 1996 book "Cats Are Not Peas: A Calico History of Genetics". Sadly while it seems to be ready available, it is very expensive.
posted by lefty lucky cat at 3:14 PM on March 1, 2015 [1 favorite]

There are very few courses where more cats wouldn't improve everything.
posted by jeather at 3:21 PM on March 1, 2015 [3 favorites]

There are very few courses where more cats wouldn't improve everything.

Even in the 15th century.
posted by adept256 at 3:30 PM on March 1, 2015 [2 favorites]

Can two blue-eyed biological parents have a brown eyed child?
posted by BrotherCaine at 3:35 PM on March 1, 2015

There are very few courses where more cats wouldn't improve everything.

That's why I always order chef's choice.
posted by 7segment at 4:13 PM on March 1, 2015 [1 favorite]

Oh shit, are we going to run out of hair coloring in 100 years?

We're mere decades from Peak Bleach.
posted by Pope Guilty at 4:25 PM on March 1, 2015 [3 favorites]

OH god we're not going to run out of blondes, why is it that no matter how often I teach Hardy-Weinberg equilibria and double heterozygote crosses, this never seems to penetrate? Recessive alleles stay in the population unless they are selected against!! Two brunettes can have a blonde baby!

Great post. I found this website a couple years back when I was fed up with having to teach the FaketyFake genetics of which thumb is on top when you put your hands together and who can roll their tongue let's see. The last straw was when I realized that the data that all this stuff is based on came originally from the Eugenics Record Office. Their conclusions about which traits were dominant/recessive rested on the ratios of the traits in a few different populations.

So I ran out and bought a Cat Fancy magazine (RIP!) and cut out all the kitties and had the students figure out the genetics of their cats' coat colors, and then mate their cats, and then we tried to figure out what lineages could give us what particular kinds of cats.

Cat genetics has everything. Multi-allele complex dominance systems--burmese/tonkinese/siamese/albino blue eyes/albino pink eyes; complex sex-linked loci (phaeomelanin and eumelanin are both on the X chromosome which is why you typically only get female calico/tortoise shell cats); pleiotropic effects (the "W" locus that causes all-white cats also causes deafness); single phenotypes caused by multiple different genes (there are three ways to get a white cat)... it was awesome. Who doesn't love pictures of cats?

(Well, it turned out one kid didn't... probably genetic.)
posted by Made of Star Stuff at 5:43 PM on March 1, 2015 [17 favorites]

Can two blue-eyed biological parents have a brown eyed child?

Yes, according to the site!

I actually looked that up a few months ago because I was reading some trashy-ish book in which a brown-eyed character had two blue-eyed parents and I thought, "That's not even biologically possible!" and felt very superior, then I thought to double-check myself and discovered I had been taught incorrectly and so didn't feel superior any more, but I was glad to have learned more about genetics.
posted by jaguar at 5:44 PM on March 1, 2015 [1 favorite]

Segundus: You might be thinking about PTC tasting, though? Where you have the piece of paper and some people taste bitterness and some people taste nothing? That is a simple Mendelian trait, basically, yes -- it's one that we can pin down to a particular protein-coding sequence of DNA, and the recessive allele is a simple loss of function mutation.
posted by Made of Star Stuff at 5:46 PM on March 1, 2015

jaguar: "because I was reading some trashy-ish book in which a brown-eyed character had two blue-eyed parents"

Was it Game of Thrones?
posted by Eyebrows McGee at 5:56 PM on March 1, 2015 [2 favorites]

Was it Game of Thrones?

No, because I've never read or seen it. *ducks* I don't actually remember what it was, but I do remember being annoyed at the author for a number of inconsistencies because I thought the eye-color thing was one more to add to the list.
posted by jaguar at 6:00 PM on March 1, 2015

OH god we're not going to run out of blondes, why is it that no matter how often I teach Hardy-Weinberg equilibria and double heterozygote crosses, this never seems to penetrate? Recessive alleles stay in the population unless they are selected against!!

I know. My (blonde) college gf would always insist on the "running out of blondes" thing and it drove me crazy that I couldn't convince her otherwise. Just trollin' ya.
posted by Navelgazer at 6:06 PM on March 1, 2015 [1 favorite]

Unfortunately, many of the papers on asparagus urine are short and lack detail. [link]

I haven't been through it all yet, but any website that contains that sentence is worth a thorough reading.
posted by mark k at 6:34 PM on March 1, 2015 [3 favorites]

If you get burned out on white cats, the polled (hornless) locus in cattle works the same way: P is dominant and produces the polled phenotype, but it is at a low frequency in many breeds of cattle (<1% in Holsteins). Most animals in the population are pp (horned), but are carriers of the recessive allele.
posted by wintermind at 7:31 PM on March 1, 2015 [1 favorite]

What are some of the simple, easily observable, inheritable traits that would make problems for teachers via the ~4%?
posted by Mitheral at 8:06 PM on March 1, 2015

Wait, some people pee pink after eating beets?! I had no idea.

On the other hand, resistance to norovirus (the incredibly contagious "stomach flu") is genetic [pubmed, review, wikipedia]. If you were ok while all the other kids were vomiting in school, you probably have a nonsense mutation in both copies of your fucosyltransferase gene.
posted by Westringia F. at 8:12 PM on March 1, 2015 [3 favorites]

Wait, some people pee pink after eating beets?! I had no idea.

I have multiple, not-that-far-apart instances in which I go to the bathroom and freak out due to pink urine, then remember I just ate roasted beets. For some reason, that knowledge does not seem to exist in my brain as a "This is something that happens to me," but as a "This is something that happens to some people sometimes" that requires several levels of processing before I remember it always happens to me.
posted by jaguar at 8:21 PM on March 1, 2015 [3 favorites]

On the beet-urine topic, I had no idea that other people didn't have this, or that it was a genetic issue. My poor theoretical future children are going to have the same panic response as me every time they eat beets, then ("OH GOD I'M DYING, oh wait, nevermind.")

This is a great article, though. I've encountered a sadly large number of "lie-to-children" lessons in science teaching, especially when I worked in a science summer camp one year. It's frustrating when concepts are simplified to the point of falsity, because how is the next generation supposed to trust scientific theories if we're teaching them bunk?

I'm also glad that the solution involves kittehs.
posted by Paper rabies at 8:40 PM on March 1, 2015 [1 favorite]

It's not blood, it's beets.
posted by en forme de poire at 12:35 AM on March 2, 2015 [2 favorites]

This doesn't have much to do with genetics, but the blue/brown eye color reminded me of this explanation about eye color:

There are two layers to the iris, the anterior and the external, or front and back layers. To produce blue eyes, there is no pigment found in the front layer. The brown pigment melanin is deposited in the back layer only. It appears blue because of reflection and diffraction of light.
posted by ana scoot at 12:41 AM on March 2, 2015

Yeah it's sort of revealing that basically every example given for the dominant/regressive paradigm is actually not one. I agree that it's not quite lies to children: Newtonian physics and the simplified version of the atom are not actually terrible depictions of the world. But many of these will make one make wildly incorrect predictions! A better lie to children would be to say blood works on mendelian inheritance (it does, right? My biology knowledge is scant), and then later on one could talk about all the exceptions that exist.
posted by Cannon Fodder at 7:51 AM on March 2, 2015

A better lie to children would be to say blood works on mendelian inheritance (it does, right? My biology knowledge is scant), and then later on one could talk about all the exceptions that exist.

It does, but blood type inheritance is complicated because of a concept called codominance. Basically, there are three alleles: iA, iB, and i. iA encodes one variant of a surface protein that sits on top of your blood cells, iB another variant, and i encodes no protein at all. So if you're genotype iA i, or iA iA, you have type A blood because you're only making the A protein on your blood cells. If you're iB i or iB iB, you're type B, and if you're i i, you're type O. All well and good, except for a tricky thing with people whose genotype is iA iB, who have one allele (the iA) which produces the A protein and one allele (the iB) which produces the B protein. So they have both variants on the surface of their blood cells, which is why they end up as type AB. That doesn't fit neatly into the normal, simple dominance paradigms that we use to teach introductory genetics. Instead, it's an example of a phenomenon biologists call codominance in which some alleles can "share" dominance with each other and have individuals display both phenotype A and B at the same time.

(Blood type is actually the most common way to teach codominance in my experience because it's so familiar, but I wouldn't use it as an example of Mendelian genetics in this way. Rh factor, maybe, but fewer people know about Rh factor. The genetics class I TA with generally uses cats and in one case horses, but I'd probably use dog color genetics left to my own devices simply because I know dog color genetics very well and I also happen to know about this excellent site explaining them. In retrospect, I ought to have linked that in the FPP, too...)
posted by sciatrix at 8:08 AM on March 2, 2015

I have pondered on the genetics of my fullball more then once since I got her.

I've had vets ask me what color she is when I make appointments.. and I go what color is she not?
posted by royalsong at 8:39 AM on March 2, 2015 [5 favorites]

That's a pretty girl, royalsong!
posted by Pope Guilty at 9:08 AM on March 2, 2015 [1 favorite]

Is the author talking about a high school course or a college course? I'm asking because the human genetic course I took half a century ago in college was pretty accurate: none of this brown eyes are dominant shit.
posted by francesca too at 9:47 AM on March 2, 2015

Segundus: You might be thinking about PTC tasting, though? Where you have the piece of paper and some people taste bitterness and some people taste nothing? That is a simple Mendelian trait, basically, yes

Actually this is listed as one of the myths on this site! I think it's because while there's a small number of genes that affect PTC tasting, it's still both polygenic and quantitative.
posted by en forme de poire at 10:24 AM on March 2, 2015