There’s no fight like a family fight. Or as homicide detectives have been known to say, “Nearest and dearest has the motive with the mostest.” Oddly, this often holds in biology and ecology as well. The more closely related something is to you, the more likely it is to be competing for the resources you need to survive. Walnuts and other trees produce chemicals to prevent seedlings from growing near their roots. Birds sing and physically attack other birds of the same species to protect enough territory to survive in. Mockingbirds are opportunistically omnivorous, so they imitate every other bird they hear to chase them out. And so on.
Competition between individuals of the same species, even close relatives, starts very early; in placental mammals, pretty much from the moment of implantation. It’s hard to wax poetic about the miracle of motherhood when you know there’s actually an intense biological struggle going on between the baby and the mother for who gets what resources, how, when, and how fast. I’ll spare you the grisly details. Suffice it to say prenatal vitamins are an extremely good idea. Especially enough calcium. Eep.
Which makes you wonder how much calcium investment is saved by not having hard shells, and how the whole messy business of placental reproduction got started in the first place. The short answer to that appears to be viruses, as I’ve mentioned in other posts. But that leads to a deeper question: how did our genome integrate viruses that form masses of mostly-undifferentiated tissue without blowing up? Viruses come in DNA or RNA, and transcribe their code into RNA which then gets translated into the proteins that cause cellular havoc, but these seem to be RNA-based viruses and that doesn’t get turned back into DNA….
Or so we thought, until HIV gave us one of the first stunning counterexamples with reverse transcriptase. Ouch.
Since then we’ve discovered a host of other nasty viral tricks, but now it looks like the cellular cloak and dagger doesn’t all go one way. Mammal cells have 14 DNA polymerases, usually meant to repair DNA, copy it, or transcribe it into RNA. Researchers from Thomas Jefferson University have found that polymerase theta is absolutely lousy at normal DNA repair, but awesome at turning an RNA template into shiny new DNA, even able to change its own protein shape to fit the bulk of an RNA molecule; something the other polymerases just can’t do.
The stumper, of course, is why do we have a polymerase that will do that in the first place? It seems like a wide-open door in the middle of our high-security immune system, viruses walk right in. Worse, polymerase theta tends to be produced in large quantities in cancers, leading to their growth and drug resistance. So it’s not just a potential viral back door, it opens the gates to your own cells killing you horribly.
At this point in time nobody’s sure. Maybe it’s meant as a last-ditch repair mechanism for shattered DNA from remaining whole RNA in the cell. Nobody knows, they’re working on how to find out.
So here’s the seed for an SF plot: what might this really be good for? And what goes wrong – or right – when it clashes with genetic engineering?
Me, I’m wondering if it’s an elaborate species-wide genetic counterespionage, high-risk but potentially high-reward. If a virus comes up with something useful, maybe we steal it….