Key features of genetic code.

Genetic code is a three letters (triplets) code defining the transfer of the information from nucleic acid to proteins. Codon is a successive string of three nucleotides. Nucleotides found in human DNA are adenine (A), thymine (T), guanine (G), and cytosine (C). In RNA, thymine is replaced by uracil (U).

Genetic code has 6 main features :

1. The genetic code is degenerate : There are 20 main amino acids but they can be coded for by 64 different triplet combinations of codons. It logically means that one amino acid is coded by more than one codon. We can say that the nucleotide at last position is the least important. Some important amino acids are coded just by one codon (methionine and tryptophan). On other hand, serine is coded by 6 possible combinations.
2. The genetic code is unambiguous: This feature is related to the first point one amino acid can be coded by several different codon; however each codon only codes for one amino acid not more. Hence, the unambiguity of genetic code.
3. The genetic code is almost universal :  The genetic code is pretty similar in most of the organisms. It means that codon which codes for methionine in human does the same in prokaryotes. This point is not exactly true as recently, scientists has discovered many expectations from this rule.
4. The codon is read in mRNA in a contiguous fashion. There are no punctuations.
5. AUG has dual functions. It codes for methionine and act as start codon.
6. The codon is triplet. 61 codons code for amino acids and three codons do not code for any amino acid. Hence, they function as stop codons.