Anticodon

Anticodon

The anticodon is a sequence of three nucleotides forming a unit of genetic code in a transfer RNA (tRNA) molecule, corresponding to a complementary codon in messenger RNA (mRNA). This interaction is crucial for the translation of genetic information from mRNA into proteins, a process that occurs in the ribosome.

Structure

Each tRNA molecule has a specific anticodon that is complementary to a codon on the mRNA. The anticodon is located in the anticodon loop of the tRNA, which is a part of the tRNA's three-dimensional L-shaped structure. The anticodon loop is typically composed of seven nucleotides, with the three anticodon bases in the middle.

Function

The primary function of the anticodon is to ensure that the correct amino acid is added to the growing polypeptide chain during protein synthesis. This is achieved through base pairing between the anticodon of the tRNA and the codon of the mRNA. For example, if the mRNA codon is AUG, the anticodon on the tRNA will be UAC, allowing the tRNA to bring the amino acid methionine to the ribosome.

Wobble Hypothesis

The wobble hypothesis, proposed by Francis Crick, explains how a single tRNA can recognize multiple codons. According to this hypothesis, the base at the 5' end of the anticodon (the "wobble" position) can form non-standard base pairs with the 3' base of the codon. This flexibility allows for fewer tRNA molecules to cover all the codons for a particular amino acid.

Anticodon-Codon Interaction

The interaction between the anticodon and the codon is mediated by hydrogen bonds, similar to the base pairing seen in DNA. The specificity of this interaction is crucial for the fidelity of protein synthesis. Any errors in this process can lead to the incorporation of incorrect amino acids, potentially resulting in dysfunctional proteins.

Clinical Significance

Mutations in tRNA genes that affect the anticodon can lead to diseases. For example, mutations that alter the anticodon can cause the tRNA to misread codons, leading to the production of abnormal proteins. Such mutations have been implicated in various genetic disorders and mitochondrial diseases.

See Also

• Codon
• Transfer RNA
• Protein synthesis
• Genetic code

References

• Crick, F. H. C. (1966). "Codon—anticodon pairing: The wobble hypothesis." Journal of Molecular Biology.
• Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). "Molecular Biology of the Cell." Garland Science.