I’ve been trying to learn about mutations for a comic/universe thing I’m making up, but pretty much all the information I’ve seen is pretty poor, sometimes it’s too scientific for me to understand, and sometimes reverse-image searching leads me to more confusion. Do you know any interesting mutations in vertebrates (specifically humans but I would be happy to hear about mutations in other species!) you could talk about? I hope this message hasn’t bothered you! And thank you!
Mutation is a funny word because it can mean any “aberrant” or “random” change as minor as to one gene in your whole DNA code, so the vast majority of mutations (trillions and trillions of them a day) are microscopic and unseen.
But of course when most people think “mutations” they think extra heads and eyes and stuff, and that happens too!
In vertebrates, the appearance of additional parts is usually caused when one or more fetuses are just partially absorbed by another. The extra appendages are technically one of their siblings, and it’s still alive, but mindless, and living off the “host” bloodstream like a parasite.
(They gave the older twin that nice collar, why don’t they put cute little booties or something on the little one??)
There’s also the “cyclops” mutation, kind of the opposite, because instead of extra parts from multiple embryos, a cyclops is a single animal that failed to divide all the way during development.
Like this shark!
Sadly no cyclops we know of ever survives more than maybe a few days. The organs are all wrong and it just can’t function. Even if it could, the single eye would probably be totally blind.
The most “movie style” mutation examples that exist, though, can be found in captive fruit flies. We’ve used fruit flies to study DNA for generations now, and by messing with their genes, we’ve created all kinds of bizarre varieties.
This fly literally developed EYES INSTEAD OF LEGS.
And this one has legs instead of antennae! Face legs!
It would be more challenging, but not impossible to induce similar mutations in vertebrates, but extreme things like this – the wrong body part in entirely the wrong place – virtually never happen in nature, except in teratoma cancers, which can become clumps of eyes, teeth, organ tissues, and even tiny limbs in one tumor.
As a general rule, a “visible” mutation like these is never going to look “right” – you’ll never see a deviation with perfect, healthy looking, functional extra limbs, at the very least because the animal’s natural metabolism is set up to feed and sustain only the expected number in the expected arrangement; any more are going to remain stunted and weak.
The reason vertebrates don’t get parts “plugged into the wrong sockets” is because the layout of the body is determined by the Hox genes, and where every other animal has just one copy of each Hox gene, vertebrates have four! If something going wrong with one, it has an effect, but a much more dampened one:
This is understandable – vertebrates have incredibly complex skeletal, muscular, and vascular systems, operating at a large scale, and meant to last for a long period of time. Redundancy is pretty important here!
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