Biology – Protein synthesis | e-Consult

The universal genetic code refers to the fact that the same codons (triplets of DNA bases) specify the same amino acids in virtually all organisms, from bacteria to humans. This universality is a key piece of evidence supporting the evolutionary relationship between all living things. The code is based on the sequence of nucleotide bases (adenine, guanine, cytosine, and thymine in DNA) within a gene. Each codon consists of three bases.

How triplets code for amino acids: Each codon corresponds to a specific amino acid. This is not a one-to-one mapping; the genetic code is degenerate, meaning that multiple codons can code for the same amino acid. For example, the codon UCU, UCC, UCA, and UCG all code for Serine. This degeneracy arises from the redundancy of the genetic code. The degeneracy is thought to provide some protection against mutations, as a mutation in the DNA sequence might not always result in a change in the amino acid sequence if a synonymous codon is available.

Start and Stop Codons: Certain codons do not code for amino acids but instead serve as signals to initiate or terminate protein synthesis. The start codon is typically AUG, which codes for methionine. This codon signals the ribosome to begin translation. Stop codons (UAA, UAG, and UGA) signal the ribosome to terminate translation, releasing the newly synthesized polypeptide chain. These codons lack an amino acid stop signal and are recognized by release factors.

In summary, the universal genetic code is a fundamental principle that underlies the flow of genetic information from DNA to RNA to protein. Its universality highlights the common ancestry of all life and its degeneracy provides a degree of robustness against mutations.