Consider translation of the following mRNA sequence:
5′-...AUGCAGAUCCAUGCCUAUUGA...-3′

Diagram translation at the moment the fourth amino acid is added to the polypeptide chain. Show the ribosome; label its A, P, and E sites; show its direction of movement; and indicate the position and anticodon triplet sequence of tRNAs that are currently interacting with mRNA codons.

Key Concepts

Translation Process

Translation is the process by which ribosomes synthesize proteins using mRNA as a template. It involves decoding the mRNA sequence into a polypeptide chain, where each set of three nucleotides (codon) corresponds to a specific amino acid. The ribosome facilitates this process by providing a site for tRNA molecules to bring the appropriate amino acids, ensuring the correct sequence is formed.

Ribosome Structure and Function

The ribosome is a complex molecular machine composed of ribosomal RNA (rRNA) and proteins, consisting of two subunits: the large and small subunits. It has three key sites: the A (aminoacyl) site, where new tRNA enters; the P (peptidyl) site, where the growing polypeptide chain is held; and the E (exit) site, where empty tRNA exits. Understanding these sites is crucial for visualizing how translation occurs and how the ribosome moves along the mRNA.

tRNA and Anticodon-Codon Interaction

Transfer RNA (tRNA) molecules are responsible for bringing amino acids to the ribosome during translation. Each tRNA has an anticodon region that is complementary to a specific mRNA codon, allowing for accurate pairing. This interaction ensures that the correct amino acid is added to the growing polypeptide chain, which is essential for proper protein synthesis and function.