In this tutorial, you will learn about the process of DNA translation and how it creates proteins.
Topics Covered in Other Articles
- DNA Transcription Explained
- DNA Replication in Biology
- Deoxyribonucleic Acid (DNA)
- Central Dogma of Biology
- RNA Interference
- Nucleic Acids
What is DNA Translation?
DNA translation is the second step in creating proteins following transcription in biology. In translation, the messenger RNA (mRNA) is decoded to build a protein. The mRNA directs the addition of amino acids during protein synthesis.
Transcription vs DNA Translation
The process of transcription makes an mRNA copy of a gene sequence of the DNA. However, the process of translation sequences the mRNA molecule to the amino acid sequence in protein synthesis. Both of these processes are used by a gene to create proteins.
The Genetic Code
Since translation “reads” the information in mRNA, a set of instructions for building a polypeptide is in the RNA nucleotides. These are groups of three nucleotides called codons. There are a total of 61 codons for amino acids that specify certain proteins. Start codons signal the start of protein construction and stop codons signal when a protein is complete. If you want to learn more about the genetic code, check out this article.
Molecules Involved in Translation
Two molecules play a key role in translation: transfer RNA (tRNA) and ribosomes. Transfer RNAs connect mRNA codons to the amino acids they encode. One end of a tRNA has a sequence of three nucleotides called an anticodon, these bind to specific mRNA codons. The other end of the tRNA carries the amino acid that is specified by the codons.
A ribosome is the structures where polypeptides (proteins) are built. They are made of protein and ribosomal RNA (rRNA). A ribosome has two subunits, a large one and a small one, that form around the mRNA. The ribosome also provides slots where the tRNAs attach to their matching codons on the mRNA template. These slots are the A, P, and E sites. Ribosomes also act as an enzyme for catalyzing the reaction that links amino acids together.
Process of DNA Translation
The process of translation involves three stages: initiation, elongation, and termination. GTP and ATP drive these steps.
During the initiation phase, the ribosome attaches to the mRNA created in transcription. The ribosome will read the mRNA and attach the tRNA that is carrying the amino acid methionine. Methionine matches the start codon AUG. This then creates the initiation complex and allows translation to start.
Elongation is the stage where the amino acid chain gets longer. In elongation, the ribosome reads the mRNA one codon at a time. As a result, the matching amino acid attaches to create a growing protein chain.
When a new codon becomes exposed:
- A matching tRNA binds to the codon
- The already existing amino acid chain (polypeptide) links via a chemical reaction to the amino acid on the tRNA
- The mRNA shifts a codon over by the ribosome allowing for a new codon to be exposed for reading
During elongation, the tRNAs move through the A, P, and E sites of the ribosome. This process repeats until all the new amino acids add to the growing chain.
Termination is the final stage of translation. During termination, the polypeptide chain releases. The process begins when a stop codon enters the ribosome, this triggers a series of events that separate the chain from its tRNA. As a result, the chain drifts out of the ribosome and migrates to its destination within the cell.