What is the correct sequence of events during translation?
Elongation, initiation, termination
Initiation, elongation, termination
Initiation, elongation, initiation
Termination, elongation, initiation
The Correct Answer and Explanation is :
The correct sequence of events during translation is Initiation, elongation, termination.
Explanation:
Translation is the process by which a cell converts messenger RNA (mRNA) into a protein. This process occurs in three main stages: initiation, elongation, and termination. Here’s a breakdown of each step:
- Initiation:
- The process begins when the small ribosomal subunit binds to the mRNA. The mRNA sequence includes a start codon (AUG), which signals the beginning of the translation process.
- A transfer RNA (tRNA) molecule with the anticodon complementary to the start codon (UAC) binds to the mRNA. This tRNA carries the amino acid methionine (in eukaryotes, it’s always methionine).
- The large ribosomal subunit then attaches to form a complete ribosome. This assembly creates the translation initiation complex. The ribosome has three binding sites for tRNA: the A site (aminoacyl site), the P site (peptidyl site), and the E site (exit site).
- Elongation:
- During elongation, the ribosome moves along the mRNA, reading the codons and facilitating the addition of amino acids to the growing polypeptide chain.
- The tRNA molecules continue to bind to the ribosome at the A site. Each tRNA carries an amino acid corresponding to the codon on the mRNA.
- The ribosome catalyzes the formation of a peptide bond between the amino acid in the P site and the one in the A site.
- The ribosome then shifts along the mRNA (a process known as translocation), moving the tRNA in the P site to the E site for exit, and the tRNA in the A site to the P site. This process repeats, elongating the polypeptide chain.
- Termination:
- Termination occurs when the ribosome encounters a stop codon on the mRNA (such as UAA, UAG, or UGA).
- Release factors bind to the stop codon, prompting the ribosome to release the newly synthesized polypeptide and disassemble.
- The mRNA is also released, and the ribosomal subunits separate, completing the translation process.
Thus, the sequence of events is initiation, elongation, and termination.