If I wasn’t a writer, I think I’d like to be a genetic researcher. I know, they seem like totally unrelated fields, but hear me out. The thing that interests me most in the entire world is why people (or characters) are who they are, and what makes them tick. And one of the things at the very bottom of what makes people tick is in their genes, and I think that’s why I find genetics so interesting. I love picking out the features that I inherited from my parents (my dad’s eyes, my mum’s cheekbones) as well as those that haven’t appeared for several generations (my hair texture).
Since humans are around 99.9% genetically identical, it’s amazing to think that such a tiny percentage difference can result in such incredible variation in our species. And one of the vehicles for that variation is genetic mutation.
Unfortunately, we’re not yet mutating the power of flight or telepathy—sorry, Professor X. A mutation is a permanent change in the DNA structure of a gene. They can be inherited or acquired, and they can be beneficial, neutral or pathogenic (seldom are they superpowers). Some mutations eventually become so common that they’re considered “normal,” and then we call them polymorphs, whereas others remain rare and unusual in the human population.
Because this is a beauty site, I’ve picked seven physical mutations to write about. Some of them are considered polymorphs and some aren’t, but they all make us uniquely beautiful. And who knows—maybe someday I’ll get that adamantium skeleton I’ve been asking Santa for since I was 6.
I never thought much about my eyes growing up. They were very much like my dad’s, and I figured that having blue, yellow, and green all mixed up together was just what green eyes looked like.
Imagine my surprise to find out that this is actually quite atypical, and all thanks to a mutation called heterochromia iridum. It refers to eyes that have multiple colours in them, and you’ve probably heard of it if you’ve seen X Men: First Class; young Professor X calls it “a very groovy mutation.”
There are three types of heterochromia:
- Complete (each eye a different color).
- Sectoral (a segment of contrasting color in the iris).
- Central (a different colour radiating out from the pupil).
These three categories are pretty fluid, though, and they can combine in weird and wonderful ways. My left eye is far lighter and more yellow than my right, while my right eye has The Blotch. Both have rings of gray and yellow around the pupil.
I guess this is why I always get attitude at the DMV when I tell them my eyes are green.
If you’re born with heterochromia, it’s probably because one of your parents had it—it’s a dominant autosomal trait. Though you could also be a chimera (two fertilised eggs fusing into one zygote, each with a different gene for eye colour) or a mosaic (someone with two or more different genetic codes in their cells; in this case, a slightly altered gene responsible for eye colour).
It’s also possible to acquire heterochromia, although you probably don’t want to. It’s almost always the result of a serious illness or injury. Certain medications have been known to deposit brown pigment in eyes—a pretty rare side-effect, and one that usually only happens in hazel eyes, but certainly one worth mentioning.
Most sources I consulted say that heterochromia is super-rare, but from my very scientific study of both readers and writers, I’ve determined that it really isn’t rare at all. It seems like most of us have some form of this, with central being the most popular. Multicolored eyes, unite!
2 Double eyelashes
I had to include this after this outstanding Elizabeth Taylor tutorial, because Taylor was famous for her super-dark, gorgeous double eyelashes.
It’s called distichiasis, and if you’re born with it, it’s because one of your parents had it (it’s a dominant trait, so you’re welcome, future offspring). It’s the result of a transcription error on your 16th chromosome, and can also be a symptom of some pretty serious heart-related disorders.
This is another fun mutation expressed in my phenotype. It’s not as obvious on me as it is on some people, because my eyelashes are blonde. But man, do I ever have a lot of them.
There is a difference, though, between having “lots of eyelashes” and a double row, and it can difficult to figure out if you have this particular mutation or not. Google is very little help, except to be absolutely disgusting (seriously, is there anything grosser than gross eye pictures?). So today I’m going to be better than Web MD.
Here’s how you can tell: Lift up the lashes on your upper eyelid and peek underneath where the waterline is. If your eyelashes stop and then your waterline starts, you have beautiful thick lashes. If, however, you can see lashes sprouting out of your waterline where they should not be (I find this incredibly distressing), then congratulations, you have distichiasis.
Anecdotally, this isn’t always the super-gorgeous advantage that it sounds like. I had to have seven eyelashes that were growing in towards my eye removed when I was a kid, which, thankfully, I only have vague memories of now.
Another way to tell is to go to a new eye doctor for a checkup. If they say “Damn, what’s going on HERE?” then congratulations, and may the spirit of Liz Taylor be with you.
3 Red hair
I think most people know that red hair is a recessive trait; meaning that if you’re a ginger (term used with lots of love), you have two variant copies of a gene called MC1R on each of your 16th chromosomes. This mutation results in generally fairer skin, freckles (we’ll get to them), light-coloured eyes, issues dealing with UV light and, recent studies have suggested, a unique pain tolerance.
That’s all pretty neat, but I want to talk about a totally false idea that regains popularity every couple of years: that redheads are going extinct, and that there will be no more gingers as early as 2060.
No. Just no.
How Stuff Works debunked this very, very thoroughly: “Recessive genes can become rare but don’t disappear completely unless everyone carrying that gene dies or fails to reproduce. So while red hair may remain rare, enough people carry the gene that, barring global catastrophe, redheads should continue to appear for some time.”
So the next time your Facebook friends all start posting nonsense about the looming Gingerpocalypse, just send them a link to this article and settle their hash. Then reread Anne of Green Gables and feel pleased that all is right with the world.
I have a few freckles, and I think they are the cutest. I always wished that I had more, probably because a lot of my friends growing up had them.
And guess what causes them? Or rather, guess what partially causes them?
That’s right: mutations.
And it all has to do with cells in the skin that make pigment called melanocytes. When exposed to UV light, melanocytes produce melanin, which makes skin darker to protect our DNA. There are two main types of melanin–eumelanin and pheomelanin. Pheomelanin is less common, and it’s what gives red hair and freckles their orangey tone.
Remember a second ago when we were talking about red hair and the MC1R gene? That guy is coming back into play again here. When the MC1R gene is working normally, it turns all pheomelanin into eumelanin. This means skin tans instead of freckles, and hair is a colour other than red. But when the MC1R gene isn’t working, you get red hair and freckled skin thanks to all that lovely pheomelanin floating around.
“But Alle,” I hear you saying. “Not all people who have freckles also have red hair.”
You’re so right! Remember how we know that being a ginger is a recessive trait that needs two copies of a gene—one from each parent—to be expressed?
MCR1 is that gene! Some people have a single mutated copy of it and have no idea—but it means that not all their pheomelanin changes to eumelanin, and they still get freckles when exposed to UV light. My family hasn’t ever had any redheads in it—we’re generally either dark blondes or have black Irish hair—but I, and a few of my cousins, still have freckles. It could be that we’re carrying a single redhead gene, makin’ pheomelanin like it’s our jobs.
Or it could be something else entirely, because this only applies sometimes. Not all people with red hair have freckles (though it’s more likely) and, as we know, not all people with freckles also have red hair. Something else is afoot, but scientists don’t know what it is yet. Another gene doing something? Environment? Epigenetics? No idea!
This is a super-weird result, because it tells us that freckles are a dominant trait, being expressed even when there’s only one copy of the gene in question, but red hair itself is recessive–even though they’re both caused by the same gene. Genetics is really cool and complicated, guys.
5 Blue eyes
I know: what? Blue eyes aren’t exactly rare! But mutations don’t have to be rare—this one now appears in so much of the population that it’s considered a polymorph. But really, blue eyes are the result of a pretty recent mutation. You know, 10,000 years ago. Practically yesterday.
The first thing you gotta know is that blue eyes aren’t technically a color—they’re a lack of color. Eye colour is determined by pigments in the part of the iris called the stroma, and if there is a tiny amount of pigment there (or none at all), eyes will appear blue. A bit more pigment gives us green eyes. And if there’s heaps of pigment, eyes are brown.
The gene that’s responsible for this is called OCA2, and it controls melanin. Back in the day, all humans had brown eyes—eyes with lots of melanin pigment. One day, a nearby gene mutated and started to limit OCA2’s ability to produce melanin in the iris. This stopped melanin from coloring the eyes, leaving the stroma blue, and voila! Blue eyes appeared in the population.
In fact, scientists currently think that everyone who has blue eyes is descended from a single common individual who lived around the Black Sea 6,000 to 10,000 years ago. How’s that for neat?
6 Cleft chin
Cleft chins are caused when the two halves of the jaw bone (or muscle) don’t quite fuse properly during development. A lot of really attractive people have cleft chins, so please excuse me while I indulge in some eye candy.
Common wisdom—and also Wikipedia—states that this is a primarily dominant genetic trait.
Allow me to bust this myth.
First: not all cleft chins are exactly the same. There’s heaps of variation when it comes to size (round dimples, eg: Kirk Douglas, vs Y-shaped clefts, eg: Aaron Ekhart) and depth (very subtle vs very deep). So it’s sometimes harder than you’d think to say which chin is smooth and which isn’t.
Second: men are more frequently butt-chinned than women are, which doesn’t fit the simple dominant-recessive genetic model. A really old study (from 1939)recorded that 9.6% of German men and 4.5% of German women had cleft chins. That’s a really big difference between sexes for a trait that isn’t supposed to be sex-linked.
Another study (from 1960) found that even when two parents had smooth chins, they could still have cleft-chinned offspring. It didn’t happen often (11% of the time), but it happened. If cleft chins truly are dominant, this should have been impossible.
So basically, if Alexander Skarsgard and I ever had a kid, there’s a chance it would have a cleft chin—but it’s not a certainty.
That’s a little disappointing, honestly.
7 No-show wisdom teeth
If there’s one thing I wish would just die out of the human population, it would be wisdom teeth. Mine popped up when I was 20, all four completely on their sides, two of them poking through the gums like painful little islands in a sea of pink gum.
There’s a lot of variation when it comes to how people recover after wisdom teeth surgery–I did not have a great time. I honestly hope that not many of you guys know what dry sockets are, because they are the worst and most horrible things.
When I cursed my horrible teeth to my dad, he got really quiet and said “I never had those.”
Yep. My dad is one of the lucky ones who was born without wisdom teeth.
As things are right now, we aren’t totally sure that this is a mutation, because we’re not sure why wisdom teeth don’t show up (even though it happens in an estimated 35% of the population). Is there a gene that says “No, wisdom teeth do not grow here?” A bunch of genes? Is it due to environmental factors? Some kind of physical injury in childhood that prevents them from forming? Nobody knows for sure!
There’s some recent evidence that the suppression of wisdom teeth was a mutation that popped up in China three to four hundred THOUSAND years ago. This doesn’t prove anything, but it sure is interesting to think that my dad is possibly the beneficiary of a four-hundred-thousand-year-old mutation.
Although if the point of variation like this is to pass them down to your children, that didn’t work out very well. Both my brother and I had fully impacted wisdom teeth followed by painful surgeries and long recoveries. Womp womp.
This article originally appeared on xoJane by Alle Connell