by Hannah Thrash
If you were to ask what the most important thing to know about biology, there are a couple of different answers you might get. But chances are, one of the top things mentioned would be the Central Dogma of Biology. This central dogma, or main principle, is the foundation of molecular biology and explains why cells can operate, why organs function, and ultimately why the body works!
So what is this central dogma? The Central Dogma of Biology is the principle that DNA makes mRNA and mRNA makes proteins (Figure 1). Simple as that! But it is so vital to our understanding of biology. Let’s break it down.
Figure 1: The Central Dogma. DNA, which is double-stranded, undergoes transcription to make single-stranded mRNA. The mRNA undergoes translation to make a protein. (Figure created in Biorender by author, adapted from template image.)
Part 1: DNA makes mRNA
DNA is a double-stranded, 3D molecule that contains all the genetic information for an organism. Every cell has every piece of DNA stored in a special area of the cell called the nucleus. DNA is a blueprint, or recipe, for the cell. It has all the instructions for everything the cell is supposed to do. The problem is that DNA is stuck in its special compartment, the nucleus, and it can’t get out to the rest of the cell to tell it what to do. So, in the nucleus, DNA undergoes a process called transcription. Transcription makes a copy of the DNA, except this copy can leave the nucleus. We call this special copy of the DNA, mRNA (see also). mRNA then leaves the nucleus, carrying instructions for the cell.
Think about it like this. You go to your grandmother’s house and find her recipe for her famous chocolate chip cookies. Except this recipe isn’t allowed out of the house (this is like the DNA stuck in the nucleus). So, you decide to copy the recipe (like transcription) and take that copy home (mRNA is a copy of DNA that leaves the nucleus).
Part 2: mRNA makes Protein
So the mRNA has been created from the DNA and is now outside of the nucleus. Great! But the cell still doesn’t know how to read or act upon the instructions. This is where translation comes in. The ribosome is the site of translation in the cell. At the ribosome, a piece of mRNA is read by the ribosome and translated into a protein! This process of translation involves multiple steps, but once it is complete, a brand-new protein is formed. Now proteins are active molecules in the cell, and can perform specific jobs. Once the protein is formed, the instructions given by the DNA can actually be carried out, and the cell’s behavior can change according to what the DNA dictated initially. When a bunch of cells all change their behavior in the same way, that is enough to change what the body itself does! This is why the Central Dogma of Biology is one of the most critical concepts in biology. It is essential to explain how cells function because it links the cell’s instructions (DNA) to its actions (performed by proteins), laying the foundation for many other concepts in biology.
Back to our analogy to finish it out! You have a copy of your grandmother’s cookie recipe, or the mRNA, and it is outside her house. But when you get home, you realize that in the copying process, all the words turned into some unknown language, and you can’t read it! So you input the recipe into a translator machine (translation), and it prints out for you a brand new copy in a language and words you can understand. It even offers helpful hints on the best actions to take to make the cookies wonderful. This new copy is like your protein, something that you can act upon, and it changes your behavior – because your next move will be to start baking!
