This post is also available in podcast format on the Anchor app, which is available on IOS and Android:
All life depends on information storage and transmission. No ifs or buts. DNA is the weapon of choice these days. It carries the alphabet of life, coding for almost every single permutation of biology that exists. Once, however, it may have had a more versatile forerunner.
RNA, or ribose nucleic acid, is now relegated to worker bee status in the cell. Whilst DNA lords over it’s cellular domain, providing the instructions for just about every single activity in the cell, RNA is now involved in DNA replication, via the processes of transcription and translation. Billions of years ago, however, RNA may have been much, much more.
To explain how, I have to stray from the script a little and talk about the other major players of the cell: proteins. Think of a cell as a kitchen. Where DNA is an executive chef, pretty much doing nothing but writing menus, and telling everyone how things should be done, the proteins are the poor saps slavishly working to the chef’s bidding. Proteins are the kitchen-hands, dishwashers, line cooks and general slaves of the cell.
If you were to look at a protein, you’d wonder why. They have a crazy variety of forms. Just imagine your cat had found a ball of yarn and left a tangled web of yarn all over the floor.
Picture the tangle. That tangle is a shape, really. It’s no different to a square, or a human head or banana or one of those weird dices that Dungeons and Dragons players use. Shape is the key word here. All proteins perform a discrete function. This function is directly tied into the shape of the protein. Most proteins look something like that mess of yarn on the floor. But it goes a little deeper than that.
Ok. So shape equals function in protein. How does RNA or DNA matter here?
If you picture DNA you’re probably seeing some kind of twirly, ladder like structure. That’s pretty much what a DNA molecule is: a twisty ladder; otherwise known as a double helix. DNA’s single function: information storage, is tied into this configuration. RNA is a bit different. It’s one side of that twisty ladder, or a single strand. RNA still works well as an information storage molecule. That’s how it is involved in DNA replication. Short snippets of mRNA, or messenger RNA carry instructions vital to the whole proceeding. Viruses actually use RNA as their core genetic material, not DNA.
RNA has one extra special feature. It can fold and twist into bizarre shapes like protein can. These shapes can bestow upon some RNAs the properties of a special class of proteins called enzymes. Enzymes are catalysts, meaning essentially they just make stuff happen. They kick-start biological reactions, ensuring that the cell works at all. It’s believed that some RNAs can do this, folding and twisting into new forms which are called ribozymes.
Ribozymes are catalytic like enzymes. In the primordial brave new world of ancient Earth there were no complex cells with grand genetic machinery and a retinue of proteins doing DNA’s bidding. Life hadn’t figured out this nifty little double act yet. Back then it was the Wild West. Every bit of biological stuff floating around had to be a generalist, able to do many things: A jack of all trades if you will. RNA may have been one of these generalists. This one little ability of RNA: it’s tendency to get bent out of shape, may have been a boon to the very first life on Earth.
Anchor FM is super fun and easy to use. Download it for yourself! If I can do it, anyone can.
Whilst you’re still here, an article from fellow bloggers moosmosis outlining the central dogma of molecular biology, as alluded to in this post: