Final answer:
Aminoacyl-tRNA molecules read codons on mRNA through complementary base pairing between an anticodon and codon, initiating protein synthesis from the start codon AUG and continuing until a stop codon is reached. This process is facilitated by the wobble position and specific pairing rules, allowing a limited number of tRNAs to decode all codons for amino acids.
Step-by-step explanation:
Aminoacyl-tRNA molecules "read" the codons on mRNA through the complementary base pairing between the three-base anticodon of the tRNA and the three-base codon on the mRNA. Each tRNA molecule has its specific anticodon that binds to its complementary codon on the mRNA. For instance, a tRNA with the anticodon GGC will bind to the mRNA codon CCG. This pairing is critical in the translation process where ribosomes synthesize proteins by decoding the mRNA sequence. During translation, the ribosome binds to the mRNA and starts reading from the start codon (AUG), which also codes for methionine. This establishes the reading frame for the mRNA. tRNAs bring their attached amino acids to the ribosome, aligning their anticodons with the corresponding codons on the mRNA. When a match is found, the amino acid is added to the growing polypeptide chain. This process continues until a stop codon is reached, signaling the end of translation.
The decoding relies on specific pairing rules and flexibility at the third base of a codon, often referred to as the wobble position. For instance, inosinate (I) in tRNA anticodons can hydrogen bond with U, C, or A nucleotides at the wobble position. This allows some tRNAs to read more than one codon and is essential in understanding how a limited number of tRNAs can interpret all 61 codons that code for amino acids.