Where’d You Get Those Genes?

via deviantart.net

Where’d you get your genes?

Oh, on clearance at Penney’s.

Right!? Probably a pretty good/bad first response if a science communicator ever asked you this. Especially a TED presenter. (For some reason, those things bug me — so artificial and smug in their self-importance. “Where do your genes come from?” asks the fame-hungry scientist, stalking the stage with a headset microphone. “PENNEY’S ON CLEARANCE!!” I yell from the back row, before being escorted off the premises.)

Anyway, your GENES, of course, do not come from Penney’s. Human genetic material is one of the few things department stores do not (yet) sell. But here is an actual TEDed presentation on a question you may not have considered: how’d you get those genes that turn matter into you? A question so basic/fundamental that it is an accomplishment just to ask it.

The answer is: from just three basic sources.

Most casual laypersons know that our DNA consists of genes — packets of genetic material that convey traits. But why does DNA contain these little phenotypic missives? How did this unzippable, replicable molecule come to be segmented into the chemical equivalent of chapters (or sentences, or words)?

Here’s how the TEDed talk tells it: First, well, “it depends on the gene,” they say. “It depends” is hardly ever a satisfying answer, so let’s try to boil those “depends” down to a few (hopefully) interesting sources. Your genes come from:

1) Legacy Genes: The earliest forms of life first developed genes in order to replicate/survive, and passed them on down to you, me and Frank over the millennia. For example, genes for DNA copying.

2) Copy Errors: Speaking of DNA copying, new genes have arisen when DNA accidentally created multiple copies of a gene. The new copies could then mutate into new genes. Presto! Your genome now has both Gene Classic and New Gene. Plus, maybe Crystal Gene and Lemon-Lime Gene down the road.

3) Random Employment: Long stretches of noncoding DNA, ‘genetic gibberish,’ sits there in the genome just sort of hanging out. Sometimes, mutations make it, in fact, do something — i.e., code for a protein. If further mutations make that protein useful — new gene!

And from those three sources, all the bewildering array of functions the human and other bodies perform. One of the more interesting examples from the video: One snake’s venom originated as a chemical made in the pancreas. That gene got copied, mutated, and took a trip, ending up expressing in the fangs. Pancreatic juice did bad things to snake victims, so it turned out to be a useful change. So the snake got a venom gene.

It amounts to a lot of reshuffling. Billions and billions of years of reshuffling of text, and it seeds the planet with an incredibly rich vocabulary of genes. Including mouse-paralyzing pancreatic fang-juice.

If you’re paying attention, you’ll notice that the first answer sort of begs the original question. How were those first genes created? How did the first replicable packets of genetic material — genes — develop? It’s a lot easier to answer the question of how, once there are a few genes, new versions are formed. Once you have the basic machinery going, new widgets can come along. But that first segmenting of DNA into genes would have to arise as the genetic code mutated and evolved, and started doing discrete things on discrete stretches of itself.

There’s plenty out there on the origin of life from nonliving matter. A crucial first step is the development of replicating molecules, RNA and/or DNA. These replicating molecules would be subject to evolution, eventually. Then, you get molecules of lesser or greater fitness. And, I suppose, this could involve the kind of information-segregation that you see with genes. But it seems to me like a still somewhat mysterious step.

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