Final answer:
During protein synthesis, the ribosome begins translating mRNA when the small ribosomal subunit, initiation factors, and initiator tRNA form an initiation complex with the start codon AUG. This codon signals the start of protein translation, with methionine as the first amino acid incorporated. Transfer RNA molecules then bring in amino acids that correspond to each three-base codon on the mRNA until a stop codon indicates the end of translation.
Step-by-step explanation:
The process of translating mRNA into a sequence of amino acids during protein synthesis begins with the assembly of an initiation complex. This complex includes the small ribosomal subunit, the mRNA itself, several initiation factors, and the initiator tRNA, which is recognized by its anticodon UAG and pairs with the start codon AUG on the mRNA. This start codon signals the ribosome to begin translating the mRNA. The initiator tRNA carries the amino acid methionine, which means that methionine is the first amino acid incorporated into the nascent polypeptide chain.
As the ribosome moves along the mRNA, it reads the codons in sets of three bases. Each codon corresponds to a specific amino acid, and tRNA molecules carry the appropriate amino acids to the ribosome. The anticodon on the tRNA pairs with the mRNA codon, enabling the corresponding amino acid to be added to the growing polypeptide chain. The process continues until a stop codon is encountered, signaling the end of translation and the release of the completed polypeptide.
The ribosome, tRNA, and mRNA work together in the translation process to ensure that the genetic code is accurately converted into a functional protein. After translation, the protein may undergo folding and modification, obtaining a specific three-dimensional shape necessary for its function within the cell.