How to Translate mRNA to Amino Acids (DECODING THE GENETIC CODE)

DNA makes mRNA makes protein, and to figure out what protein a specific sequence of mRNA creates we can use a codon table. Today I’ll show you how!

The genetic code consists of 4 bases which code for 20 amino acids. The nucleotides in the mRNA are read in triplets, called codons, which means that the total number of combinations are 4 to the power of 3 or in other words 64 possible combinations. So we can read a mRNA strand from the left to the right in groups of 3. Each set of 3 or in other words, each codon codes for a specific amino acid.

The mRNA can be interpreted using a codon table or a codon wheel. We will use the same strand of mRNA in both cases for simplicity to make sure you understand the idea. Before we do anything else, we need to find a start codon and a stop codon. From the table, we can quickly notice that the start codon is AUG. The stop codon will either be UAA, UAG or UGA. For some reason thinking about a cave man helps me remember all 4 of these start and stop codons…. The space in-between the start and stop codon is known as a reading frame.

So starting with the codon table we simply read it from the left to the right. The start codon codes for methionine. The second triplet is UGC. By looking at the table here, here and here we can see that the second amino acid is cysteine. Then comes AUC, now we look here, here and here to see that the next amino acid is isoleucine.

The codon wheel is almost even more intuitive. You simply read from the center outwards. Let’s use the same example to read out the final 2 codons. So next comes CCA. By simply starting from C, going to the next C and all the way out to A, we see that the next amino acid in the chain is proline. The final codon is UGA, which you might remember since it sounds rather “cavemanlike”. Anyway, let’s read it out just to ensure that we know how to use the wheel as well. So we simply read, U to G to A to find this little square which if we look here we can see means stop.

Congratulations! You know how to use both a codon table as well as a codon wheel to successfully translate mRNA into amino acids.