The process of translation, essential for protein synthesis, unfolds in three key stages: initiation, elongation, and termination. Each of these stages mirrors the steps found in transcription, beginning with the initiation phase, which marks the start of translation.
During the initiation of translation, the small ribosomal subunit first binds to the messenger RNA (mRNA). This mRNA contains codons, which are sequences of three nucleotides that specify particular amino acids. The first codon, known as the start codon, is AUG, which codes for the amino acid methionine (abbreviated as MET). Following the binding of the small ribosomal subunit to the mRNA, a transfer RNA (tRNA) carrying methionine attaches to the start codon. The tRNA has an anticodon that is complementary to the mRNA codon, ensuring the correct amino acid is added to the growing polypeptide chain.
After the small ribosomal subunit and tRNA are in place, the large ribosomal subunit joins the complex, completing the formation of the ribosome. This assembly is facilitated by several proteins known as initiation factors, which play a crucial role in the process. Additionally, the initiation of translation requires energy, highlighting the complexity of this initial step.
At the conclusion of the initiation phase, a fully assembled ribosome is ready to begin elongation, with the first tRNA positioned at the start codon, ready to initiate the synthesis of the polypeptide chain. Understanding this process is vital as it sets the stage for the subsequent elongation and termination phases of translation.