Question

Mention the essential qualities for a universal genetic code.

Answer 1

For a genetic code to be considered universal and functional across all living organisms, it must possess the following essential qualities:

1. Triplet Nature: The code is composed of codons, each consisting of three nitrogenous bases. This provides 64 possible combinations, sufficient to code for all 20 standard amino acids.
2. Universality: The most critical quality is that the same codon codes for the same amino acid in almost all known organisms, from bacteria to humans. For example, UUU codes for Phenylalanine in all species.
3. Non-ambiguity: Each specific codon specifies only one amino acid. This ensures that the genetic message is always translated into the same protein sequence without error.
4. Degeneracy (Redundancy): Most amino acids are specified by more than one codon. This helps protect the organism by minimising the functional impact of certain mutations.
5. Non-overlapping and Commaless: The code is read sequentially, three bases at a time, without any overlapping of bases or “punctuation” (gaps) between codons.
6. Polarity: The code has a definite direction and is always read in the 5’ → 3’ direction.
7. Initiation and Termination Signals: The code includes specific “start” codons (like AUG) to begin translation and “stop” codons (like UAA, UAG, UGA) to signal the end of protein synthesis.