a key, evolving molecule by any other name…
Believe it or not, DNA is not the only hereditary molecule out there. In fact, it's one of many molecules that could form the backbone of gene pools.
When it comes to biology, everyone can name the key molecule for life as we know it. Scientists mine it for all sorts of tantalizing clues about our past and possible future while creationists effectively worship it as proof of a deity as some sort of programmer of all living things. But what if I and Ed Yong were to tell you that DNA isn’t the only molecule capable of passing down hereditary information and serving as a key mechanism for basic evolutionary changes?
In fact, there’s a whole class of so-called XNA molecules in which deoxyribose can be easily replaced with a whole host of other sugars like cyclohexane, therose, hexose, and glycol to create new kinds of hereditary molecules called CaNA, TNA, HNA, and GNA, respectively. The X in XNA is basically just a placeholder for any sugar that will form a stable helix to contain the nucleic acids to be read. Considering that so many sugars can step up to bat and create a double helix enabling living things to develop and evolve, it’s actually kind of a mystery as to why deoxyribose won out at the dawn of time and prompts one to wonder if we would still be around with say, an ANA which used arabinose instead of the DNA we know and love today?
Now, oddly, the answer seems to be yes because they function the same way and there’s no reason why we couldn’t exist with such a substitution to our cellular chemistry. It’s too late now of course because a life form using an XNA wouldn’t be able to replicate with a DNA utilizing organism. In fact, the researcher who identified these possible permutations of hereditary molecules wants to use them to safeguard us from synthetic life, making sure that it could still be hearty enough to survive competition from bacteria that have been around for billions of years while being unable to actually interfere with our current ecosystem.
And as Ed points out, the divergence doesn’t stop there as some scientists are adding even more bases to hereditary molecules to try and coax synthetic life forms into producing very unusual amino acids that would be of use to us. Now, this is all obviously pretty cool because this is quite literally tinkering with the foundations of life, both as we know it, and as we think we might know it, but what can it say about the future and the implications of this work? A very straightforward application could be in astrobiology and the probes sent to other worlds could be instructed to detect a wide array of sugars used in XNAs in soil samples, hopefully indicating some alien biota.
But there’s a potential for a different application. Today, we can engineer fairly harmless viruses which deliver small bits of interfering RNA to shut down gene expression in certain disorders, halting their progression to make them easier to treat. One of the ultimate possibilities of this siRNA technology is to keep cancer tumors in stasis, though considering the recent findings that each tumor may house more than ten different strains of harmful genetic anomalies, we need to figure out how to effectively customize them to attack all those different harmful genes first. It’s a tall order to be sure, but the important thing is that we have a plan and there’s a lot of research into this type of genetic engineering underway.
Ultimately, this could even open to door to modifying our own gene signaling to drastically improve our quality of life with age, and perhaps even increase life span by manipulating the biology complicit in making us weaker and more prone to death. Nature doesn’t have the expiration date for an organism stamped into its genome which makes it much harder to delay death, but we know that after a while, the repair of wear and tear slows and damage continues to build up until we get weak enough to be taken out by something that might not have killed us if we were younger or a vital organ starts to fail after accumulating too much damage to continue working as it is. A thorough understanding of how genes and gene expression work can help us find ways to repair or even reverse all that damage…