Genetic Code
- The genetic code is the collection of base sequences (called as codons) that corresponds to each amino acid and to stop signals for translation.
- Since there are 20 amino acids, there must be more than 20 codons to include signals for starting and stopping the synthesis of particular protein molecules.
- If one assumes that all codons have the same number of bases, then each codon must contain at least three bases. Because: A single base cannot be a codon since there are 20 amino acids and only 4 bases.
- Pairs of bases also cannot serve as codons because there are only 42 = 16 possible pairs of four bases.
- Triplets of bases are possible because there are 43 = 64 triplets, which is more than adequate.
- In many cases, several codons designate the same amino acid- that is the code is redundant or degenerate.
- In the in vitro system, protein synthesis can start at any base.
- However, in vivo it starts only at AUG codon. Similarly it stops at either UAA, UGA or UAG.
The universal genetic code
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Last modified: Wednesday, 28 March 2012, 11:26 PM