DNA, otherwise formally known as Deoxyribonucleic Acid.
It’s one of the most important, unifying parts of biology (at least for biology on Earth) that almost everyone on Planet Earth is aware of. (Yes, I’m talking to YOU in particular. You know who you are.) Denying its crucial place in biology is like trying to convince everyone that the sky isn’t blue— there’s just no logical way to do it.
Most people know that when something happens to your genes or inside your body, DNA is usually at the center of it. DNA, as it turns out, is actually a sort of “guidebook” in your cell on how to make these things called proteins that are important in their own right; they are responsible for just about everything that happens inside your body. If you can think of a function, DNA, and the proteins that it leads to, is probably connected to it in some way.
Tackling a nasty infection? Yep, DNA has the genes to create proteins called “antibodies” that will fight off those disgusting bacteria for you. Is your cell lacking energy? DNA creates enzymes that will break down the sugars and turn them into ATP in a process called “Cellular Respiration”. (Metaphor for that coming soon) The process of creating proteins from DNA is called Protein Synthesis, and the concept has often been referred to as the Central Dogma of Biology. I learned the hard way that this has nothing to do with dogs.
The entire process of turning DNA into a protein, however, is quite the journey. There are several different steps involved in making proteins, which are long and complex… sort of like film production. In a lot of ways, the cell is like a movie studio creating a diverse range of proteins (movies) that spread out across the cell, driving forward the cell’s processes, the same way that movies contribute to our culture.
So let’s start at the beginning.
The production of the movie begins… in the cell, which acts as our movie studio. Obviously, the cell is a very complex thing that is divisible into many other parts, each of which has its own special contribution to make to the synthesis of proteins or the creation of the movie.
But before you can create a Hollywood-level masterpiece, before you can start shooting your different scenes, before you can find actors to play in your show… You first need an idea and a script. Someone needs to write the instructions for what each actor says, what motions they do, what roles they have, alongside props and any other sets that may help in production. You need something that serves as a blueprint for how the movie will unfold, and that is the initial role DNA will fill. DNA is, well, a script for your cells to follow in the creation of proteins. Except that DNA isn’t just one script. But rather, think of it as a huge filing cabinet with hundreds, if not thousands, of scripts, each for an entirely different movie. In fact, it contains all of the blueprints for proteins that you’ll ever need— proteins have pretty much every function imaginable, and DNA accounts for every part of it— from hormones that make you depressed (like me, who’s in 5 APs) to antibodies that make up nasty infections. This part of the cell is called the Nucleus; an entire organelle dedicated to storing our DNA. Every possible movie that the studio could make is stored in a script somewhere in this massive archive that complements the DNA of the cell. In the movie studio, this could kind of be like the library, having every single genre of a movie imaginable, from thrillers to comedy to documentaries, and potentially even one that will turn my older fictional writings into a movie. (all the movie companies out there… I’m begging you. Please.)
Eventually, the cell decides that it wants to create a very specific movie (or protein) and starts embarking on the path to protein synthesis. So now that the studio has picked this movie for production, it needs to be sent outside to the rest of the studio. No one is going to be producing a movie if only one script exists, which is why the copying machine will come in quite handy. The DNA has to stay inside the nucleus, so something else needs to actually be able to transfer that information outside so that proteins can actually start being made.
The copymaker is an analogy for RNA Polymerase, an enzyme that transcribes DNA (the script) into RNA (the copies), helping our movie production further along. This RNA will later serve as the very template for the creation of the actual scenes of the protein’s creation. The RNA polymerase goes along through the DNA, taking each of its individual base pairs and complementing them in the structure of the RNA that it creates, effectively making the same blueprint for the movie’s creation as what the DNA has. The biological process in which RNA Polymerase creates the script is called Transcription.
But just like my articles, the first draft isn’t perfect. First movie drafts contain a lot of errors; maybe they don’t have a title page complete yet. Maybe when being presented, they simply need a protective folder to protect against water spills. (which I am particularly prone to doing) Maybe it’s full of scenes that don’t actually contribute to the overall plot of the movie. This is definitely the case with the RNA that we’ve now created. Yeah, it’s an exact copy of the DNA script, but that certainly doesn’t mean we’re ready to just ship it off outside of the nucleus and start shooting some scenes. The RNA needs to go through some Post-Transcriptional Modifications to ensure that it is completely ready to start being turned into a protein.
First off, the RNA that we’ve copied straight from the DNA has a lot of these things called Introns; they’re basically parts of that RNA that don’t actually contribute to the plot. There are a lot of deleted scenes in movies that don’t make it to the final cut; why? Because they don’t really add to the overall plot, and as a result, they’re removed. When we make a protein, we want to be completely sure that everything we’re building in the protein genuinely contributes to that structure. In a long RNA strand, you could have vast amounts of these unneeded base pairs that need to be removed. It turns out that the Nucleus has this thing called the Spliceosome that can take out the parts that you don’t need and reattach what are called exons, the part of the RNA that actually codes for something, into an improved RNA script.
After these key revisions have been made, one more problem needs to be faced; a lot is going on in a cell outside of the Nucleus. What if someone spills their orange juice on the script, ruining it past the point of repair? What if it’s lost or stolen? In a more biological sense, what if another molecule comes by the RNA and inadvertently reacts with it, causing it to deform?
Well, there are a couple of special mechanisms that the cell has that allow it to keep its RNA safe. The RNA is capped off with a 5’ cap and a poly-A tail, similar to how our copies are fitted with a title page and a protective folder.
With our script done, we can finally begin shooting our film — but that’s not going to occur in the nucleus, where we only have piles and piles of scripts and copy machines. Who would want to make a movie there? But don’t worry; there’s a very special facility that our movie studio cell has that is perfect for the construction of proteins! It’s called the Ribosome, and it will basically act as our shooting set. This is the part where the script, after all of the hard work our writers have put into it, sees the light of day, and the production of the actual film is about to begin.
The ribosome will read the RNA (our script) in codons (units of 3 nucleic acids), paralleling how movie directors will read the script to understand which actors to hire. Once the RNA is read, the ribosome now officially knows which kind of actors it wants to bring to the film set. These actors are basically amino acids— the building blocks of proteins. There are twenty different kinds of amino acids, each of which has its own role that it can contribute to the story. Hundreds of these amino acids stack on top of one another to create the scenes for a complex, sophisticated movie. The process in which the mRNA is translated into a chain of long amino acids is called… well, translation.
Every movie is different; as stated before, there are different genres, storylines, and characters to just about every single one. Proteins are the same— they have a unique variety of structures that lead to a variety of different functions. But all movies start the same way: with that title in front depicting the movie’s name. It turns out there’s a very specific start codon called AUG, which complements the amino acid called Methionine, or Met. In every movie, a title scene gets the ball rolling with the movie. Met is what gets the production of that long amino acid chain going.
But you’re not just going to have actors immediately on the spot and ready to start filming. The film production ribosome needs to go out and actually recruit them; the public wants to see a movie being made quickly, or they’ll start to grow impatient. (Yes, you are guilty of this, too, in some way.)
In fact, it has a special team that’s already prepared to go about recruiting everything needed. There’s this thing called tRNA, an RNA type that is specialized in going out and finding certain amino acids and bringing them back so that they can be used in the movie, just like how movies will go and recruit actors to come and play their role in the acting scene for them. (And yes, this is 100% done out of their own free will. No need to sue them.)
And now that all the amino acids have finally arrived at the ribosome, it’s finally time to start making a protein! The actors begin to hit the ground running, interacting with each other in seas of conversation and actions, like how amino acids form peptide bonds with each other, contributing to the protein’s creation. Scenes are piling up and being shot left and right, and we are now finally seeing the formation of the real movie itself. Once the RNA is translated, there is only one step left before the actual protein, or movie, is finished. We’ve just got a whole bunch of raw footage, but movies typically contain far more than just that average raw footage. You need to edit those amino acids to make sure that they are one hundred percent ready for the public to experience. The movie studio works through its last major step, making sure the final product is as high-quality as possible, so the public will give it more money.
The scenes are edited together to make a smooth viewing experience, as each scene begins to link together into one coherent story, like how the long line of amino acids becomes a folded protein. Protein folding is the final step in the creation of a protein, and there’s only one last thing to do with it.
That’s right! Our movie needs to be sold, viewed, and enjoyed by millions of people in the world. Advertisements, sponsors, and marketing all culminate in putting our movie out there. In the biological world, the protein can undergo post-transcriptional modifications, such as phosphorylation, allowing the protein to be induced, making the protein fully functional, and able to be used in any of its designated processes. Every single day, every second, even millions of cells inside your body are constantly hard at work, spending their resources creating all of these films for your body to be able to use to survive to the next day, even if you can’t see it. So the next time you’re watching a movie, remember what your cells spend all their time working on to keep you alive.
It’s a long life of hard work for them.
Below is a far more detailed supplemental pages about the steps of Protein Synthesis if you’re interested: