Wolverine vs. Multiple Man: Comparing DNA repair and replication

Wolverine vs. Multiple Man: Comparing DNA repair and replication

Wolverine is a much-loved hero of the Marvel X-men universe. The wolverine has his retractable claws and his adamantium-reinforced skeleton, but as any true fan knows, it’s not really the adamantium that makes wolverine so tough. It’s his ability to do repair. Punch him, stab him or put a bullet in him, Wolverine has the magical ability to quickly and correctly repair himself. This makes Wolverine essentially immortal. The latest Wolverine comic has the hero dying, showing that he may have some weakness, but I predict he’ll come back somehow.  

Multiple Man is a less well known bad guy from the same universe. Multiple Man has the power to make copies or “dupes” or himself. It takes as little energy as snapping his fingers to make a new dupe and the duplicates are perfect copies. With this ability, he can multi-task like no other and can even reabsorb a dupe and gain all of the knowledge and experiences that the dupe acquired.  However, each dupe is mortal and can be killed. Nonetheless, with the ability to produce an army with a snap of his fingers, Multiple Man is also quite powerful.

So if we imagine a battle between these two characters, with one that can repair almost any damage and the other that can copy himself to vast numbers we have an epic battle between replication and repair. I don’t know if this stand off has actually happened in the comics, but given his popularity, pretty much everyone predicts that Wolverine would win. However, if you ask biology students the question “What’s more important for the cell, repair or replication?” They will universally answer: Replication.

Without replication, they argue, an organism could never produce offspring. There would be no mitosis, no meiosis, no daughter cells of any kind. Without replication, extinction would be inevitable. Life without replication hardly seems like living at all.  On the other hand, without repair you could still replicate. The only side effect, the argument continues, would be that evolution would happen faster if there was no repair.

The reality of life is that without DNA repair, death would come much faster than without DNA replication. Perhaps it’s the way that biology is taught: Cell division,  DNA structure and Evolution (at least in most classrooms) are put right up front. Repair isn’t really explained until college level courses.  It’s easy to see why someone might think that repair is trivial. That DNA must be perfectly stable in that pristine double helix we always see. And that cancer, when it happens, is the result of one unlucky exposure to a carcinogen. 

The following chart gives an estimate for the amount of DNA damage that each cell in the body must endure everyday. The numbers are staggering. Each cell must survive thousands upon thousands of damaging events each day. Radiation, carcinogens, even our own metabolisms cause damage and yet each cell has the magical ability to quickly and correctly repair itself.  Each cell is a little Wolverine.

Doctor who and the scary prokarote

It's always tough when one of your favorite television shows blows the science. For me it makes it difficult, if not impossible, to enjoy the rest of the show. Case in point, this weeks Doctor Who, which is a huge favorite of mine, laid a giant, big, bad science goose egg with the episode "Kill the Moon".

Some mild spoilers to follow after the logo below, so be warned.

In this episode, the Doctor comes across a recently deceased giant spider of an alien. It looks very menacing, it attacks one of the main characters (big mistake) and it subsequently dies.  This is all quite normal for the show. You expect there to be scary aliens. You expect the Doctor, as a time-travelling uber-genious, to give all of us some helpful background on all of the scary aliens he bumps into. But you don't expect a line like this:

"It’s the size of a badger! It’s a prokaryotic unicellular life form with non-chromosomal DNA, which as you and me know, yes, scientists know--this is a GERM!"

Ugh. There's so much wrong with this statement, it's painful. So, let's start with the part that's ok. Prokaryotic is a misnomer, as the name (pre-nucleus) implies that organisms without nuclei are awaiting the nuclei they someday hope to have. They're not. But that's not that bad, even the textbooks cling to that mistake. And I like the way Peter Capaldi says "prokaryotic."

But a unicellular life form the size of a badger? That looks suspiciously like a well known invertebrate with teeth? That part grates on the science nerves. There are some strang unicellular life forms deep in the ocean, such as xenophyphores, that can reach the tremendous size of up to 4 inches long. This is pretty impressive, but they're the size of a golf pencil, not a badger.

 And, this is a Eukaryote, the largest bacterium -- ok, prokaryote for now -- is Thiomargarita thamibiensis. This prokaryote can reach 0.75 mm, which is huge for a little cell, but still no bigger than the size of a pin head. 

Xenophyphores, giant unicellular life, if 4 inches fits your definition of giant.

This too I think I can handle, because who knows maybe there ARE large unicellular life forms out there. The “biggest” label should correctly be the “biggest currently known.” So, ok my teeth were clenching and then the final “non-chromosomal DNA” sets in. Why, Doctor? All prokaryotes have chromosomal DNA, their DNA is non-nuclear but it’s still chromosomal.

Here’s hoping the next time the Doctor runs into these spider-germs he says, “These spiders are the size of badgers! And they’re attacking like germs do on Earth.” That be fine.  Just fine. Despite, the science rant, I will be watching the next episode – where the scary alien is a mummy!