Note (12/2015): Hi there! I'm taking some time off here to focus on other projects for a bit. As of October 2016, those other projects include a science book series for kids titled Things That Make You Go Yuck! -- available at Barnes and Noble, Amazon and (hopefully) a bookstore near you!

Co-author Jenn Dlugos and I are also doing some extremely ridiculous things over at Drinkstorm Studios, including our award-winning webseries, Magicland.

There are also a full 100 posts right here in the archives, and feel free to drop me a line at with comments, suggestions or wacky cold fusion ideas. Cheers!

· Categories: Biology, Genetics
What I’ve Learned:

Junk DNA: there's a whole lotta junk in ALL of our trunks.
“Junk DNA: there’s a whole lotta junk in ALL of our trunks.”

Comparing yourself with other people is tricky. George Carlin famously pointed out that “their stuff is shit, but your shit is stuff“. Which is great, if you’re comparing music collections or wardrobes or childrens’ refrigerator art.

But there’s another thing we have in common with other people: our DNA. And when it comes to genetic material, it turns out everybody’s is mostly junk. Yes, even yours. And George Carlin’s.

(Well, at this point, certainly George Carlin’s. Unless you count half of Kelly Carlin. Which you probably should.)

But don’t feel too bad about your junky genome. “You are what you eat,” as the saying goes — so if you’ve ever shoveled down a McRib or a whole bag of powdered mini donuts down your gullet, then you knew some “junk” was probably in there, somewhere.

The question is… how much? No one is entirely sure.

Regrettable food choices aside, the degree of “junkitude” in a species’ DNA was first measured in a very simple way. Somewhere within that DNA are a number of genes — regions that are transcribed into RNA messages, and then translated into proteins, which perform most every function in living cells.

Different species have different sized genomes, and varying numbers of genes. Back in the ’60s or so, scientists took a hard line concerning “junk DNA”: if it can produce a protein, it’s useful. If not? Junk.

That leaves many species with an awful lot of so-called junk DNA — and it makes humans look like downright hoarders. Using this definition, roughly 98% of our DNA is pointless garbage. Expired Fruitopia coupons. Porky’s Revenge Betamax tapes. Last year’s newspapers. Or really, any newspapers.

But a funny thing happened on the way to our deoxyribonucleic intervention. As scientists dug deeper into how our genomes work, they discovered something interesting. Our non-protein-coding DNA may be “junk” — but that junk DNA… is not.

Not junk, that is. At least, some of it isn’t. Because while genes — actual, protein-producing sequences — only make up about 2% of our DNA, other regions are pretty important, too. Like telomeres, for instance — little fiddly bits of DNA that “cap” chromosomes to protect the squishy ends. Or for that matter, centromeres — repetitive sequences where two halves of each chromosome are held together, and which are critical during cell division.

But it’s not just structural elements hiding in the junk DNA. There’s other stuff in that shit, too. Thousands of regulatory sites, for instance. All those protein-encoding genes are great — but on their own, they’re kind of dumb. If you don’t want intestine genes turned on in your brain, or adrenaline released along with melatonin — and seriously, you do not — then something has to regulate how and when and where and why each gene gets expressed.

That “something” is a bunch of proteins, mostly — but they do their jobs by sitting down on stretches of non-coding DNA to direct traffic. Take away those “junk” DNA regions, and your gene expression suddenly goes all higgledy-piggledy. Congratulations, spring cleaner. You’re a sewer mutant now.

There are other important things happening in our “junk” DNA, but we’re still discovering what all of them are. Maybe 10% of our DNA is actually useful. Or 8.2%, according to one study. Maybe as much as 50%. But probably not more than that; nearly half our DNA is thought to come from transposable elements and integrated viruses, which are generally not so useful.

So Carlin wasn’t wrong, but he didn’t have the whole story. True, our shit is stuff, and their stuff is shit. But underneath, we’re all 50 to 98% junk. Sorta makes you want to mutter the seven words you can never say on television, dunnit?

Image sources: Biotechnology and Society (junk DNA), Amazing Spaces (Carlin, finding a place for his stuff), YouTube (powdered donut face), Daily Beast (sewer muties, wavin’)

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· Categories: Biology, Genetics
What I’ve Learned:

Splice junctions: snipping ads out of your favorite programs since many millions of years ago.
“Splice junctions: snipping ads out of your favorite programs since many millions of years ago.”

Your DNA is crap.

Well, mostly it’s crap. But so is mine, and so is everyone else’s. For all the wondrous and amazing things our genetic code can accomplish, most of the really good stuff comes from a tiny little fraction of the genome. The rest is poorly understood, variable in quality and dubious in value.

In other words, your DNA is like cable TV.

Think of it this way: imagine all of your genetic material — three billion DNA base pairs tucked into every one of your cells, and responsible for making you “you” and not me or a goldfish or a head of iceberg lettuce — laid out in a line, like a TV program schedule. The “shows” are the genes — twenty to thirty thousand snippets of code that actually mean something. These can be read to produce proteins, which do just about all of the important work in your body, from grabbing the oxygen you breathe to growing toenails to helping you decide how much of that Buffy the Vampire Slayer marathon to sit through.

(All of it. Duh.)

But what’s between those shows you like, in the great abyss of “five hundred channels and nothing on”? Well, a couple of things. First, there are “pseudogenes” — stretches of DNA that look like they might do something interesting, but which have been mutated and mangled past the point of being useful. These are your knockoff shows and half-assed sequels: Who Wants to Be a Thousandaire?. Seinfarb. Home Alone 9: The Alonening. No good can come from these, clearly.

There are other bits of fluff, too. Near-endless repeats — possibly important in DNA for structure; used in TV as an excuse for USA to cram another NCIS rerun on the schedule. And long, droning stretches of apparently random sequence — the overnight informercials of the human genome.

But back to the genes. These are structured like TV shows in another important way: our genes contain commercials. In the genome, these are called “introns”, and are bits of DNA in between the important parts (which are called “exons”). When the gene is finally translated into a protein, these bits are snipped out in a process called splicing. And the edges of each intron in the line contain a short code called a splice junction, which tells the translation machinery where to snip the nonsense out.

So if a gene is like a television show, then a spliced gene is like watching with TiVo. Which is clearly better, because you can skip the commercials. And it’s made possible at the genetic level by splice junctions.

These splice junctions are tiny two-base sequences — usually GU (in RNA-speak) on one end, and AG on the other — that mark the intron they surround for snipping. But it’s not always a simple matter of lopping out the “commercials”. Many of our genes undergo a process called alternative splicing, where chunks containing multiple introns (and the exons between them) can be yanked out, producing multiple proteins from the same gene — sometimes with very different functions.

Think of alternative splicing as watching through the setup of, say, your favorite cop drama, then skipping to the end when they catch the perp. All that stuff in the middle is just filler and dusting for fingerprints, right? Much better.

So the next time your body translates a gene into a protein — which is all the time, obviously — give a little thanks to the splicing, and splice junctions, that make it possible, by editing out the crap in your cable lineup of a genome.

And then get back to that Buffython. Season 5 isn’t gonna watch itself, sunshine.

Image sources: Wikipedia (splicing), The Mental Elf (TV watcher), Uncoached and TimeToast (intron-snipping TiVos), Jack of All Trades… (Buffy squeal)

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