What is RNA?

The Central Dogma of Molecular Biology Controls the flow of information.

You’ve probably heard about DNA (DeoxyriboNucleic Acid), and know that it is the blueprint or instructions to build all the parts of us (skin, hair, muscle, etc.), which are mostly made of protein. You get half of your DNA from your mom and half from your dad in the form of chromosomes, the units of heredity. Our chromosomes are organized into genes-about 20,000 genes in humans, to be exact-where each gene carries the code for a specific protein. In simpler terms, you can think of DNA as a cherished family cookbook, where each recipe is a gene, and the proteins are the delicious pie or cake the recipes (genes) instruct you to make.

DNA and RNA have similar “alphabets,” but protein is a different language

DNA and RNA are both types of biological molecules known as “nucleic acid.” They are each made of four different building blocks (nucleotides) that make up a code. For DNA, the nucleotides are A (Adenine), T (Thymine), G (Guanine), and C (Cytosine). For RNA, the letters are the same, except RNA uses U (Uracil), instead of T in its code. Another difference in the building blocks of DNA vs. RNA is that different “sugar” molecules are used, but we won’t focus on that part for now. Finally, the DNA that makes up our chromosomes generally exists as a double-helix or double-stranded molecule. This means that two individual chains of DNA interact with each other, where A likes to pair with T and G likes to pair with C in a process called “base pairing.” RNA, on the other hand is more of a solitary molecule, and is generally found in a single stranded state, although RNA is creative and can perform some molecular gymnastics to pair with itself.

Now you’ve learned about the Central Dogma, and how DNA the it is the blueprint to make proteins, using RNA as a messenger.

​But does RNA do anything else? Being a messenger seems pretty boring.

Well, actually, RNA comes in many other sizes and forms that do different jobs in all our cells, and in fact, most forms of RNA in cells DO NOT build proteins!

For instance, ribosomal and transfer RNAs (rRNA and tRNA) help in the process of making proteins. Ribosomes are the cellular machines or factories made of protein and rRNA that actually build the proteins, and tRNAs are like the secret decoder ring that reads the language of RNA and turns it into proteins! (See why it’s called translation?) Other RNAs help to correctly package the mRNAs in the nucleus in a process called splicing. Yet other RNAs (really small ones called microRNAs) can turn mRNAs on or off, providing fine tuning of when and where proteins are made in the cell. AND, there are many more types of RNA that we don’t have time to talk about here. In the end, our cells would not function without this alphabet soup of RNA molecules.

COVID-19 vaccines have put RNA in the spotlight, but how do they work?

You’ve probably heard a lot about the COVID-19 mRNA vaccines. These vaccines were a revolutionary RNA technology and opened the door to using RNA vaccines for many types of infectious diseases (in humans and in livestock) as well as cancer. So how does this work? Well, a piece of mRNA (yellow) encoding a protein that we want our bodies to raise an immune response against is introduced into our bodies, carried in a tiny protective case or shell called a “nanoparticle.” The nanoparticle fuses to our cells, delivering the mRNA to the inside of our cells, where our own cellular machinery (ribosomes! tRNAs!) will make the protein encoded by the mRNA. From there, the protein is shipped outside of the cells, and our immune system recognizes it as a “foreign” protein, which sets off alarm bells. This causes the body to generate antibodies and immune cells that remember the foreign protein and attack it if the protein is ever encountered again. Amazing, right?