Genetic Code
By Chandana Valaboju | 3 September 2024
The genetic code refers to the sequence of instructions contained in a gene. The instructions aid in forming peptide bonds between corresponding amino acids, which later fold to give proteins. The flow of information happens from DNA to mRNA to proteins. This is called the Central Dogma of Molecular Biology.
The information is stored in DNA by the sequence in which nucleotide bases are arranged. After transcription of DNA, the mRNA formed moves to the ribosomes. A combination of three nucleotide bases together is called a codons and corresponds to a particular amino acid. tRNA (transfer RNA) binds to each codon and brings the corresponding amino acid along with it, during the process of translation.
There are 64 possible codon sequences, out of which 61 correspond to an amino acid and the other three are stop codons (UAA, UAG, UGA), which don’t get translated and signal the end of the translation process. The AUG codon has a dual purpose – it codes for methionine and acts as an initiator codon, that is, it signals the beginning of translation.
The genetic code is said to be degenerate, because a single amino acid can be coded for by more than one codon. The genetic code is nearly universal for all organisms, with only rare variations ever detected (like in some mitochondrial codons and some protozoans).
The genetic code, outlining which codon corresponds to which amino acid, is given below.
References:
- James D Watson, Tania Baker, Stephen Bell, Alexander Gann, Michael Levine, Richard Losick, Molecular Biology of the Gene, India: Affiliated East West Press, 2024
- Koji Tamura. (2016, Aug 25). The Genetic Code: Francis Crick’s Legacy and Beyond. National Library of Medicine.
- Image: OpenOregon