How does translation depend on complementary base-pairing between mRNA codons and tRNA anticodons?

SouravNovember 8, 2024

Answer

Translation is a critical biological process that synthesizes polypeptides (proteins) from messenger RNA (mRNA) sequences. This process relies heavily on the complementary base-pairing between mRNA codons and transfer RNA (tRNA) anticodons, ensuring the correct amino acids are added to the growing polypeptide chain.

Codon-Anticodon Interaction

1. Definition of Codons and Anticodons:
   • Codons are sequences of three nucleotides in mRNA that specify a particular amino acid or signal termination of translation. For example, the codon AUG codes for methionine and also serves as the start codon.
   • Anticodons are complementary sequences of three nucleotides found in tRNA molecules. Each tRNA has an anticodon that pairs with a specific mRNA codon during translation, ensuring that the correct amino acid is incorporated into the polypeptide chain.
2. Complementary Base-Pairing:
   • The pairing between codons and anticodons follows strict base-pairing rules: adenine (A) pairs with uracil (U) in RNA, and cytosine (C) pairs with guanine (G). This complementary nature allows tRNAs to recognize and bind to their corresponding mRNA codons at the ribosome.
   • The alignment of the codon-anticodon pairs is antiparallel, meaning that the tRNA anticodon reads the mRNA codon in the opposite direction. For instance, if an mRNA codon is 5′-AUG-3′, the corresponding tRNA anticodon will be 3′-UAC-5′.

Role in Translation

1. Initiation of Translation:
   • Translation begins when the ribosome assembles around the mRNA. The small ribosomal subunit binds to the mRNA and locates the start codon (AUG). An initiator tRNA carrying methionine binds to this start codon via its anticodon.
2. Elongation Phase:
   • During elongation, tRNAs continue to bring amino acids to the ribosome as it moves along the mRNA. Each incoming tRNA pairs its anticodon with the next codon on the mRNA strand, ensuring that the appropriate amino acid is added to the growing polypeptide chain.
   • The ribosome facilitates peptide bond formation between adjacent amino acids, linking them into a polypeptide chain. This process relies on accurate codon-anticodon pairing to maintain fidelity in protein synthesis .
3. Termination:
   • Translation terminates when a stop codon is reached on the mRNA. Since there are no corresponding tRNAs for stop codons, release factors bind to the ribosome, prompting it to release the completed polypeptide.

Importance of Complementary Base-Pairing

The complementary base-pairing between mRNA codons and tRNA anticodons is essential for several reasons:

• Accuracy: This pairing ensures that each amino acid added corresponds precisely to its coding sequence in mRNA, maintaining the integrity of protein synthesis.
• Redundancy: The genetic code’s redundancy allows multiple codons to code for a single amino acid. This flexibility is facilitated by tRNAs that can recognize more than one codon due to wobble base-pairing at the third position of the codon .
• Efficiency: The ability of tRNAs to pair with specific mRNA codons allows translation to proceed efficiently, enabling rapid protein synthesis necessary for cellular function.